feat(dir2config): defaults

vendor/gopkg.in/src-d/go-git.v4/plumbing/format/config/common.go

@@ -0,0 +1,99 @@
+package config
+
+// New creates a new config instance.
+func New() *Config {
+	return &Config{}
+}
+
+// Config contains all the sections, comments and includes from a config file.
+type Config struct {
+	Comment  *Comment
+	Sections Sections
+	Includes Includes
+}
+
+// Includes is a list of Includes in a config file.
+type Includes []*Include
+
+// Include is a reference to an included config file.
+type Include struct {
+	Path   string
+	Config *Config
+}
+
+// Comment string without the prefix '#' or ';'.
+type Comment string
+
+const (
+	// NoSubsection token is passed to Config.Section and Config.SetSection to
+	// represent the absence of a section.
+	NoSubsection = ""
+)
+
+// Section returns a existing section with the given name or creates a new one.
+func (c *Config) Section(name string) *Section {
+	for i := len(c.Sections) - 1; i >= 0; i-- {
+		s := c.Sections[i]
+		if s.IsName(name) {
+			return s
+		}
+	}
+
+	s := &Section{Name: name}
+	c.Sections = append(c.Sections, s)
+	return s
+}
+
+// AddOption adds an option to a given section and subsection. Use the
+// NoSubsection constant for the subsection argument if no subsection is wanted.
+func (c *Config) AddOption(section string, subsection string, key string, value string) *Config {
+	if subsection == "" {
+		c.Section(section).AddOption(key, value)
+	} else {
+		c.Section(section).Subsection(subsection).AddOption(key, value)
+	}
+
+	return c
+}
+
+// SetOption sets an option to a given section and subsection. Use the
+// NoSubsection constant for the subsection argument if no subsection is wanted.
+func (c *Config) SetOption(section string, subsection string, key string, value string) *Config {
+	if subsection == "" {
+		c.Section(section).SetOption(key, value)
+	} else {
+		c.Section(section).Subsection(subsection).SetOption(key, value)
+	}
+
+	return c
+}
+
+// RemoveSection removes a section from a config file.
+func (c *Config) RemoveSection(name string) *Config {
+	result := Sections{}
+	for _, s := range c.Sections {
+		if !s.IsName(name) {
+			result = append(result, s)
+		}
+	}
+
+	c.Sections = result
+	return c
+}
+
+// RemoveSubsection remove	s a subsection from a config file.
+func (c *Config) RemoveSubsection(section string, subsection string) *Config {
+	for _, s := range c.Sections {
+		if s.IsName(section) {
+			result := Subsections{}
+			for _, ss := range s.Subsections {
+				if !ss.IsName(subsection) {
+					result = append(result, ss)
+				}
+			}
+			s.Subsections = result
+		}
+	}
+
+	return c
+}

vendor/gopkg.in/src-d/go-git.v4/plumbing/format/config/decoder.go

@@ -0,0 +1,37 @@
+package config
+
+import (
+	"io"
+
+	"github.com/src-d/gcfg"
+)
+
+// A Decoder reads and decodes config files from an input stream.
+type Decoder struct {
+	io.Reader
+}
+
+// NewDecoder returns a new decoder that reads from r.
+func NewDecoder(r io.Reader) *Decoder {
+	return &Decoder{r}
+}
+
+// Decode reads the whole config from its input and stores it in the
+// value pointed to by config.
+func (d *Decoder) Decode(config *Config) error {
+	cb := func(s string, ss string, k string, v string, bv bool) error {
+		if ss == "" && k == "" {
+			config.Section(s)
+			return nil
+		}
+
+		if ss != "" && k == "" {
+			config.Section(s).Subsection(ss)
+			return nil
+		}
+
+		config.AddOption(s, ss, k, v)
+		return nil
+	}
+	return gcfg.ReadWithCallback(d, cb)
+}

vendor/gopkg.in/src-d/go-git.v4/plumbing/format/config/doc.go

@@ -0,0 +1,122 @@
+// Package config implements encoding and decoding of git config files.
+//
+// 	Configuration File
+// 	------------------
+//
+// 	The Git configuration file contains a number of variables that affect
+// 	the Git commands' behavior. The `.git/config` file in each repository
+// 	is used to store the configuration for that repository, and
+// 	`$HOME/.gitconfig` is used to store a per-user configuration as
+// 	fallback values for the `.git/config` file. The file `/etc/gitconfig`
+// 	can be used to store a system-wide default configuration.
+//
+// 	The configuration variables are used by both the Git plumbing
+// 	and the porcelains. The variables are divided into sections, wherein
+// 	the fully qualified variable name of the variable itself is the last
+// 	dot-separated segment and the section name is everything before the last
+// 	dot. The variable names are case-insensitive, allow only alphanumeric
+// 	characters and `-`, and must start with an alphabetic character.  Some
+// 	variables may appear multiple times; we say then that the variable is
+// 	multivalued.
+//
+// 	Syntax
+// 	~~~~~~
+//
+// 	The syntax is fairly flexible and permissive; whitespaces are mostly
+// 	ignored.  The '#' and ';' characters begin comments to the end of line,
+// 	blank lines are ignored.
+//
+// 	The file consists of sections and variables.  A section begins with
+// 	the name of the section in square brackets and continues until the next
+// 	section begins.  Section names are case-insensitive.  Only alphanumeric
+// 	characters, `-` and `.` are allowed in section names.  Each variable
+// 	must belong to some section, which means that there must be a section
+// 	header before the first setting of a variable.
+//
+// 	Sections can be further divided into subsections.  To begin a subsection
+// 	put its name in double quotes, separated by space from the section name,
+// 	in the section header, like in the example below:
+//
+// 	--------
+// 		[section "subsection"]
+//
+// 	--------
+//
+// 	Subsection names are case sensitive and can contain any characters except
+// 	newline (doublequote `"` and backslash can be included by escaping them
+// 	as `\"` and `\\`, respectively).  Section headers cannot span multiple
+// 	lines.  Variables may belong directly to a section or to a given subsection.
+// 	You can have `[section]` if you have `[section "subsection"]`, but you
+// 	don't need to.
+//
+// 	There is also a deprecated `[section.subsection]` syntax. With this
+// 	syntax, the subsection name is converted to lower-case and is also
+// 	compared case sensitively. These subsection names follow the same
+// 	restrictions as section names.
+//
+// 	All the other lines (and the remainder of the line after the section
+// 	header) are recognized as setting variables, in the form
+// 	'name = value' (or just 'name', which is a short-hand to say that
+// 	the variable is the boolean "true").
+// 	The variable names are case-insensitive, allow only alphanumeric characters
+// 	and `-`, and must start with an alphabetic character.
+//
+// 	A line that defines a value can be continued to the next line by
+// 	ending it with a `\`; the backquote and the end-of-line are
+// 	stripped.  Leading whitespaces after 'name =', the remainder of the
+// 	line after the first comment character '#' or ';', and trailing
+// 	whitespaces of the line are discarded unless they are enclosed in
+// 	double quotes.  Internal whitespaces within the value are retained
+// 	verbatim.
+//
+// 	Inside double quotes, double quote `"` and backslash `\` characters
+// 	must be escaped: use `\"` for `"` and `\\` for `\`.
+//
+// 	The following escape sequences (beside `\"` and `\\`) are recognized:
+// 	`\n` for newline character (NL), `\t` for horizontal tabulation (HT, TAB)
+// 	and `\b` for backspace (BS).  Other char escape sequences (including octal
+// 	escape sequences) are invalid.
+//
+// 	Includes
+// 	~~~~~~~~
+//
+// 	You can include one config file from another by setting the special
+// 	`include.path` variable to the name of the file to be included. The
+// 	variable takes a pathname as its value, and is subject to tilde
+// 	expansion.
+//
+// 	The included file is expanded immediately, as if its contents had been
+// 	found at the location of the include directive. If the value of the
+// 	`include.path` variable is a relative path, the path is considered to be
+// 	relative to the configuration file in which the include directive was
+// 	found.  See below for examples.
+//
+//
+// 	Example
+// 	~~~~~~~
+//
+// 		# Core variables
+// 		[core]
+// 			; Don't trust file modes
+// 			filemode = false
+//
+// 		# Our diff algorithm
+// 		[diff]
+// 			external = /usr/local/bin/diff-wrapper
+// 			renames = true
+//
+// 		[branch "devel"]
+// 			remote = origin
+// 			merge = refs/heads/devel
+//
+// 		# Proxy settings
+// 		[core]
+// 			gitProxy="ssh" for "kernel.org"
+// 			gitProxy=default-proxy ; for the rest
+//
+// 		[include]
+// 			path = /path/to/foo.inc ; include by absolute path
+// 			path = foo ; expand "foo" relative to the current file
+// 			path = ~/foo ; expand "foo" in your `$HOME` directory
+//
+package config

vendor/gopkg.in/src-d/go-git.v4/plumbing/format/config/encoder.go

@@ -0,0 +1,77 @@
+package config
+
+import (
+	"fmt"
+	"io"
+	"strings"
+)
+
+// An Encoder writes config files to an output stream.
+type Encoder struct {
+	w io.Writer
+}
+
+// NewEncoder returns a new encoder that writes to w.
+func NewEncoder(w io.Writer) *Encoder {
+	return &Encoder{w}
+}
+
+// Encode writes the config in git config format to the stream of the encoder.
+func (e *Encoder) Encode(cfg *Config) error {
+	for _, s := range cfg.Sections {
+		if err := e.encodeSection(s); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func (e *Encoder) encodeSection(s *Section) error {
+	if len(s.Options) > 0 {
+		if err := e.printf("[%s]\n", s.Name); err != nil {
+			return err
+		}
+
+		if err := e.encodeOptions(s.Options); err != nil {
+			return err
+		}
+	}
+
+	for _, ss := range s.Subsections {
+		if err := e.encodeSubsection(s.Name, ss); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func (e *Encoder) encodeSubsection(sectionName string, s *Subsection) error {
+	//TODO: escape
+	if err := e.printf("[%s \"%s\"]\n", sectionName, s.Name); err != nil {
+		return err
+	}
+
+	return e.encodeOptions(s.Options)
+}
+
+func (e *Encoder) encodeOptions(opts Options) error {
+	for _, o := range opts {
+		pattern := "\t%s = %s\n"
+		if strings.Contains(o.Value, "\\") {
+			pattern = "\t%s = %q\n"
+		}
+
+		if err := e.printf(pattern, o.Key, o.Value); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func (e *Encoder) printf(msg string, args ...interface{}) error {
+	_, err := fmt.Fprintf(e.w, msg, args...)
+	return err
+}

vendor/gopkg.in/src-d/go-git.v4/plumbing/format/config/option.go

@@ -0,0 +1,117 @@
+package config
+
+import (
+	"fmt"
+	"strings"
+)
+
+// Option defines a key/value entity in a config file.
+type Option struct {
+	// Key preserving original caseness.
+	// Use IsKey instead to compare key regardless of caseness.
+	Key string
+	// Original value as string, could be not normalized.
+	Value string
+}
+
+type Options []*Option
+
+// IsKey returns true if the given key matches
+// this option's key in a case-insensitive comparison.
+func (o *Option) IsKey(key string) bool {
+	return strings.ToLower(o.Key) == strings.ToLower(key)
+}
+
+func (opts Options) GoString() string {
+	var strs []string
+	for _, opt := range opts {
+		strs = append(strs, fmt.Sprintf("%#v", opt))
+	}
+
+	return strings.Join(strs, ", ")
+}
+
+// Get gets the value for the given key if set,
+// otherwise it returns the empty string.
+//
+// Note that there is no difference
+//
+// This matches git behaviour since git v1.8.1-rc1,
+// if there are multiple definitions of a key, the
+// last one wins.
+//
+// See: http://article.gmane.org/gmane.linux.kernel/1407184
+//
+// In order to get all possible values for the same key,
+// use GetAll.
+func (opts Options) Get(key string) string {
+	for i := len(opts) - 1; i >= 0; i-- {
+		o := opts[i]
+		if o.IsKey(key) {
+			return o.Value
+		}
+	}
+	return ""
+}
+
+// GetAll returns all possible values for the same key.
+func (opts Options) GetAll(key string) []string {
+	result := []string{}
+	for _, o := range opts {
+		if o.IsKey(key) {
+			result = append(result, o.Value)
+		}
+	}
+	return result
+}
+
+func (opts Options) withoutOption(key string) Options {
+	result := Options{}
+	for _, o := range opts {
+		if !o.IsKey(key) {
+			result = append(result, o)
+		}
+	}
+	return result
+}
+
+func (opts Options) withAddedOption(key string, value string) Options {
+	return append(opts, &Option{key, value})
+}
+
+func (opts Options) withSettedOption(key string, values ...string) Options {
+	var result Options
+	var added []string
+	for _, o := range opts {
+		if !o.IsKey(key) {
+			result = append(result, o)
+			continue
+		}
+
+		if contains(values, o.Value) {
+			added = append(added, o.Value)
+			result = append(result, o)
+			continue
+		}
+	}
+
+	for _, value := range values {
+		if contains(added, value) {
+			continue
+		}
+
+		result = result.withAddedOption(key, value)
+	}
+
+	return result
+}
+
+func contains(haystack []string, needle string) bool {
+	for _, s := range haystack {
+		if s == needle {
+			return true
+		}
+	}
+
+	return false
+}

vendor/gopkg.in/src-d/go-git.v4/plumbing/format/config/section.go

@@ -0,0 +1,146 @@
+package config
+
+import (
+	"fmt"
+	"strings"
+)
+
+// Section is the representation of a section inside git configuration files.
+// Each Section contains Options that are used by both the Git plumbing
+// and the porcelains.
+// Sections can be further divided into subsections. To begin a subsection
+// put its name in double quotes, separated by space from the section name,
+// in the section header, like in the example below:
+//
+//     [section "subsection"]
+//
+// All the other lines (and the remainder of the line after the section header)
+// are recognized as option variables, in the form "name = value" (or just name,
+// which is a short-hand to say that the variable is the boolean "true").
+// The variable names are case-insensitive, allow only alphanumeric characters
+// and -, and must start with an alphabetic character:
+//
+//     [section "subsection1"]
+//         option1 = value1
+//         option2
+//     [section "subsection2"]
+//         option3 = value2
+//
+type Section struct {
+	Name        string
+	Options     Options
+	Subsections Subsections
+}
+
+type Subsection struct {
+	Name    string
+	Options Options
+}
+
+type Sections []*Section
+
+func (s Sections) GoString() string {
+	var strs []string
+	for _, ss := range s {
+		strs = append(strs, fmt.Sprintf("%#v", ss))
+	}
+
+	return strings.Join(strs, ", ")
+}
+
+type Subsections []*Subsection
+
+func (s Subsections) GoString() string {
+	var strs []string
+	for _, ss := range s {
+		strs = append(strs, fmt.Sprintf("%#v", ss))
+	}
+
+	return strings.Join(strs, ", ")
+}
+
+// IsName checks if the name provided is equals to the Section name, case insensitive.
+func (s *Section) IsName(name string) bool {
+	return strings.ToLower(s.Name) == strings.ToLower(name)
+}
+
+// Option return the value for the specified key. Empty string is returned if
+// key does not exists.
+func (s *Section) Option(key string) string {
+	return s.Options.Get(key)
+}
+
+// AddOption adds a new Option to the Section. The updated Section is returned.
+func (s *Section) AddOption(key string, value string) *Section {
+	s.Options = s.Options.withAddedOption(key, value)
+	return s
+}
+
+// SetOption adds a new Option to the Section. If the option already exists, is replaced.
+// The updated Section is returned.
+func (s *Section) SetOption(key string, value string) *Section {
+	s.Options = s.Options.withSettedOption(key, value)
+	return s
+}
+
+// Remove an option with the specified key. The updated Section is returned.
+func (s *Section) RemoveOption(key string) *Section {
+	s.Options = s.Options.withoutOption(key)
+	return s
+}
+
+// Subsection returns a Subsection from the specified Section. If the
+// Subsection does not exists, new one is created and added to Section.
+func (s *Section) Subsection(name string) *Subsection {
+	for i := len(s.Subsections) - 1; i >= 0; i-- {
+		ss := s.Subsections[i]
+		if ss.IsName(name) {
+			return ss
+		}
+	}
+
+	ss := &Subsection{Name: name}
+	s.Subsections = append(s.Subsections, ss)
+	return ss
+}
+
+// HasSubsection checks if the Section has a Subsection with the specified name.
+func (s *Section) HasSubsection(name string) bool {
+	for _, ss := range s.Subsections {
+		if ss.IsName(name) {
+			return true
+		}
+	}
+
+	return false
+}
+
+// IsName checks if the name of the subsection is exactly the specified name.
+func (s *Subsection) IsName(name string) bool {
+	return s.Name == name
+}
+
+// Option returns an option with the specified key. If the option does not exists,
+// empty spring will be returned.
+func (s *Subsection) Option(key string) string {
+	return s.Options.Get(key)
+}
+
+// AddOption adds a new Option to the Subsection. The updated Subsection is returned.
+func (s *Subsection) AddOption(key string, value string) *Subsection {
+	s.Options = s.Options.withAddedOption(key, value)
+	return s
+}
+
+// SetOption adds a new Option to the Subsection. If the option already exists, is replaced.
+// The updated Subsection is returned.
+func (s *Subsection) SetOption(key string, value ...string) *Subsection {
+	s.Options = s.Options.withSettedOption(key, value...)
+	return s
+}
+
+// RemoveOption removes the option with the specified key. The updated Subsection is returned.
+func (s *Subsection) RemoveOption(key string) *Subsection {
+	s.Options = s.Options.withoutOption(key)
+	return s
+}

vendor/gopkg.in/src-d/go-git.v4/plumbing/format/diff/patch.go

@@ -0,0 +1,58 @@
+package diff
+
+import (
+	"gopkg.in/src-d/go-git.v4/plumbing"
+	"gopkg.in/src-d/go-git.v4/plumbing/filemode"
+)
+
+// Operation defines the operation of a diff item.
+type Operation int
+
+const (
+	// Equal item represents a equals diff.
+	Equal Operation = iota
+	// Add item represents an insert diff.
+	Add
+	// Delete item represents a delete diff.
+	Delete
+)
+
+// Patch represents a collection of steps to transform several files.
+type Patch interface {
+	// FilePatches returns a slice of patches per file.
+	FilePatches() []FilePatch
+	// Message returns an optional message that can be at the top of the
+	// Patch representation.
+	Message() string
+}
+
+// FilePatch represents the necessary steps to transform one file to another.
+type FilePatch interface {
+	// IsBinary returns true if this patch is representing a binary file.
+	IsBinary() bool
+	// Files returns the from and to Files, with all the necessary metadata to
+	// about them. If the patch creates a new file, "from" will be nil.
+	// If the patch deletes a file, "to" will be nil.
+	Files() (from, to File)
+	// Chunks returns a slice of ordered changes to transform "from" File to
+	// "to" File. If the file is a binary one, Chunks will be empty.
+	Chunks() []Chunk
+}
+
+// File contains all the file metadata necessary to print some patch formats.
+type File interface {
+	// Hash returns the File Hash.
+	Hash() plumbing.Hash
+	// Mode returns the FileMode.
+	Mode() filemode.FileMode
+	// Path returns the complete Path to the file, including the filename.
+	Path() string
+}
+
+// Chunk represents a portion of a file transformation to another.
+type Chunk interface {
+	// Content contains the portion of the file.
+	Content() string
+	// Type contains the Operation to do with this Chunk.
+	Type() Operation
+}

vendor/gopkg.in/src-d/go-git.v4/plumbing/format/diff/unified_encoder.go

@@ -0,0 +1,360 @@
+package diff
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"strings"
+
+	"gopkg.in/src-d/go-git.v4/plumbing"
+)
+
+const (
+	diffInit = "diff --git a/%s b/%s\n"
+
+	chunkStart  = "@@ -"
+	chunkMiddle = " +"
+	chunkEnd    = " @@%s\n"
+	chunkCount  = "%d,%d"
+
+	noFilePath = "/dev/null"
+	aDir       = "a/"
+	bDir       = "b/"
+
+	fPath  = "--- %s\n"
+	tPath  = "+++ %s\n"
+	binary = "Binary files %s and %s differ\n"
+
+	addLine    = "+%s\n"
+	deleteLine = "-%s\n"
+	equalLine  = " %s\n"
+
+	oldMode         = "old mode %o\n"
+	newMode         = "new mode %o\n"
+	deletedFileMode = "deleted file mode %o\n"
+	newFileMode     = "new file mode %o\n"
+
+	renameFrom     = "from"
+	renameTo       = "to"
+	renameFileMode = "rename %s %s\n"
+
+	indexAndMode = "index %s..%s %o\n"
+	indexNoMode  = "index %s..%s\n"
+
+	DefaultContextLines = 3
+)
+
+// UnifiedEncoder encodes an unified diff into the provided Writer.
+// There are some unsupported features:
+//     - Similarity index for renames
+//     - Sort hash representation
+type UnifiedEncoder struct {
+	io.Writer
+
+	// ctxLines is the count of unchanged lines that will appear
+	// surrounding a change.
+	ctxLines int
+
+	buf bytes.Buffer
+}
+
+func NewUnifiedEncoder(w io.Writer, ctxLines int) *UnifiedEncoder {
+	return &UnifiedEncoder{ctxLines: ctxLines, Writer: w}
+}
+
+func (e *UnifiedEncoder) Encode(patch Patch) error {
+	e.printMessage(patch.Message())
+
+	if err := e.encodeFilePatch(patch.FilePatches()); err != nil {
+		return err
+	}
+
+	_, err := e.buf.WriteTo(e)
+
+	return err
+}
+
+func (e *UnifiedEncoder) encodeFilePatch(filePatches []FilePatch) error {
+	for _, p := range filePatches {
+		f, t := p.Files()
+		if err := e.header(f, t, p.IsBinary()); err != nil {
+			return err
+		}
+
+		g := newHunksGenerator(p.Chunks(), e.ctxLines)
+		for _, c := range g.Generate() {
+			c.WriteTo(&e.buf)
+		}
+	}
+
+	return nil
+}
+
+func (e *UnifiedEncoder) printMessage(message string) {
+	isEmpty := message == ""
+	hasSuffix := strings.HasSuffix(message, "\n")
+	if !isEmpty && !hasSuffix {
+		message = message + "\n"
+	}
+
+	e.buf.WriteString(message)
+}
+
+func (e *UnifiedEncoder) header(from, to File, isBinary bool) error {
+	switch {
+	case from == nil && to == nil:
+		return nil
+	case from != nil && to != nil:
+		hashEquals := from.Hash() == to.Hash()
+
+		fmt.Fprintf(&e.buf, diffInit, from.Path(), to.Path())
+
+		if from.Mode() != to.Mode() {
+			fmt.Fprintf(&e.buf, oldMode+newMode, from.Mode(), to.Mode())
+		}
+
+		if from.Path() != to.Path() {
+			fmt.Fprintf(&e.buf,
+				renameFileMode+renameFileMode,
+				renameFrom, from.Path(), renameTo, to.Path())
+		}
+
+		if from.Mode() != to.Mode() && !hashEquals {
+			fmt.Fprintf(&e.buf, indexNoMode, from.Hash(), to.Hash())
+		} else if !hashEquals {
+			fmt.Fprintf(&e.buf, indexAndMode, from.Hash(), to.Hash(), from.Mode())
+		}
+
+		if !hashEquals {
+			e.pathLines(isBinary, aDir+from.Path(), bDir+to.Path())
+		}
+	case from == nil:
+		fmt.Fprintf(&e.buf, diffInit, to.Path(), to.Path())
+		fmt.Fprintf(&e.buf, newFileMode, to.Mode())
+		fmt.Fprintf(&e.buf, indexNoMode, plumbing.ZeroHash, to.Hash())
+		e.pathLines(isBinary, noFilePath, bDir+to.Path())
+	case to == nil:
+		fmt.Fprintf(&e.buf, diffInit, from.Path(), from.Path())
+		fmt.Fprintf(&e.buf, deletedFileMode, from.Mode())
+		fmt.Fprintf(&e.buf, indexNoMode, from.Hash(), plumbing.ZeroHash)
+		e.pathLines(isBinary, aDir+from.Path(), noFilePath)
+	}
+
+	return nil
+}
+
+func (e *UnifiedEncoder) pathLines(isBinary bool, fromPath, toPath string) {
+	format := fPath + tPath
+	if isBinary {
+		format = binary
+	}
+
+	fmt.Fprintf(&e.buf, format, fromPath, toPath)
+}
+
+type hunksGenerator struct {
+	fromLine, toLine            int
+	ctxLines                    int
+	chunks                      []Chunk
+	current                     *hunk
+	hunks                       []*hunk
+	beforeContext, afterContext []string
+}
+
+func newHunksGenerator(chunks []Chunk, ctxLines int) *hunksGenerator {
+	return &hunksGenerator{
+		chunks:   chunks,
+		ctxLines: ctxLines,
+	}
+}
+
+func (c *hunksGenerator) Generate() []*hunk {
+	for i, chunk := range c.chunks {
+		ls := splitLines(chunk.Content())
+		lsLen := len(ls)
+
+		switch chunk.Type() {
+		case Equal:
+			c.fromLine += lsLen
+			c.toLine += lsLen
+			c.processEqualsLines(ls, i)
+		case Delete:
+			if lsLen != 0 {
+				c.fromLine++
+			}
+
+			c.processHunk(i, chunk.Type())
+			c.fromLine += lsLen - 1
+			c.current.AddOp(chunk.Type(), ls...)
+		case Add:
+			if lsLen != 0 {
+				c.toLine++
+			}
+			c.processHunk(i, chunk.Type())
+			c.toLine += lsLen - 1
+			c.current.AddOp(chunk.Type(), ls...)
+		}
+
+		if i == len(c.chunks)-1 && c.current != nil {
+			c.hunks = append(c.hunks, c.current)
+		}
+	}
+
+	return c.hunks
+}
+
+func (c *hunksGenerator) processHunk(i int, op Operation) {
+	if c.current != nil {
+		return
+	}
+
+	var ctxPrefix string
+	linesBefore := len(c.beforeContext)
+	if linesBefore > c.ctxLines {
+		ctxPrefix = " " + c.beforeContext[linesBefore-c.ctxLines-1]
+		c.beforeContext = c.beforeContext[linesBefore-c.ctxLines:]
+		linesBefore = c.ctxLines
+	}
+
+	c.current = &hunk{ctxPrefix: ctxPrefix}
+	c.current.AddOp(Equal, c.beforeContext...)
+
+	switch op {
+	case Delete:
+		c.current.fromLine, c.current.toLine =
+			c.addLineNumbers(c.fromLine, c.toLine, linesBefore, i, Add)
+	case Add:
+		c.current.toLine, c.current.fromLine =
+			c.addLineNumbers(c.toLine, c.fromLine, linesBefore, i, Delete)
+	}
+
+	c.beforeContext = nil
+}
+
+// addLineNumbers obtains the line numbers in a new chunk
+func (c *hunksGenerator) addLineNumbers(la, lb int, linesBefore int, i int, op Operation) (cla, clb int) {
+	cla = la - linesBefore
+	// we need to search for a reference for the next diff
+	switch {
+	case linesBefore != 0 && c.ctxLines != 0:
+		if lb > c.ctxLines {
+			clb = lb - c.ctxLines + 1
+		} else {
+			clb = 1
+		}
+	case c.ctxLines == 0:
+		clb = lb
+	case i != len(c.chunks)-1:
+		next := c.chunks[i+1]
+		if next.Type() == op || next.Type() == Equal {
+			// this diff will be into this chunk
+			clb = lb + 1
+		}
+	}
+
+	return
+}
+
+func (c *hunksGenerator) processEqualsLines(ls []string, i int) {
+	if c.current == nil {
+		c.beforeContext = append(c.beforeContext, ls...)
+		return
+	}
+
+	c.afterContext = append(c.afterContext, ls...)
+	if len(c.afterContext) <= c.ctxLines*2 && i != len(c.chunks)-1 {
+		c.current.AddOp(Equal, c.afterContext...)
+		c.afterContext = nil
+	} else {
+		ctxLines := c.ctxLines
+		if ctxLines > len(c.afterContext) {
+			ctxLines = len(c.afterContext)
+		}
+		c.current.AddOp(Equal, c.afterContext[:ctxLines]...)
+		c.hunks = append(c.hunks, c.current)
+
+		c.current = nil
+		c.beforeContext = c.afterContext[ctxLines:]
+		c.afterContext = nil
+	}
+}
+
+func splitLines(s string) []string {
+	out := strings.Split(s, "\n")
+	if out[len(out)-1] == "" {
+		out = out[:len(out)-1]
+	}
+
+	return out
+}
+
+type hunk struct {
+	fromLine int
+	toLine   int
+
+	fromCount int
+	toCount   int
+
+	ctxPrefix string
+	ops       []*op
+}
+
+func (c *hunk) WriteTo(buf *bytes.Buffer) {
+	buf.WriteString(chunkStart)
+
+	if c.fromCount == 1 {
+		fmt.Fprintf(buf, "%d", c.fromLine)
+	} else {
+		fmt.Fprintf(buf, chunkCount, c.fromLine, c.fromCount)
+	}
+
+	buf.WriteString(chunkMiddle)
+
+	if c.toCount == 1 {
+		fmt.Fprintf(buf, "%d", c.toLine)
+	} else {
+		fmt.Fprintf(buf, chunkCount, c.toLine, c.toCount)
+	}
+
+	fmt.Fprintf(buf, chunkEnd, c.ctxPrefix)
+
+	for _, d := range c.ops {
+		buf.WriteString(d.String())
+	}
+}
+
+func (c *hunk) AddOp(t Operation, s ...string) {
+	ls := len(s)
+	switch t {
+	case Add:
+		c.toCount += ls
+	case Delete:
+		c.fromCount += ls
+	case Equal:
+		c.toCount += ls
+		c.fromCount += ls
+	}
+
+	for _, l := range s {
+		c.ops = append(c.ops, &op{l, t})
+	}
+}
+
+type op struct {
+	text string
+	t    Operation
+}
+
+func (o *op) String() string {
+	var prefix string
+	switch o.t {
+	case Add:
+		prefix = addLine
+	case Delete:
+		prefix = deleteLine
+	case Equal:
+		prefix = equalLine
+	}
+
+	return fmt.Sprintf(prefix, o.text)
+}

vendor/gopkg.in/src-d/go-git.v4/plumbing/format/gitignore/dir.go

@@ -0,0 +1,136 @@
+package gitignore
+
+import (
+	"bytes"
+	"io/ioutil"
+	"os"
+	"os/user"
+	"strings"
+
+	"gopkg.in/src-d/go-billy.v4"
+	"gopkg.in/src-d/go-git.v4/plumbing/format/config"
+	gioutil "gopkg.in/src-d/go-git.v4/utils/ioutil"
+)
+
+const (
+	commentPrefix = "#"
+	coreSection   = "core"
+	eol           = "\n"
+	excludesfile  = "excludesfile"
+	gitDir        = ".git"
+	gitignoreFile = ".gitignore"
+	gitconfigFile = ".gitconfig"
+	systemFile    = "/etc/gitconfig"
+)
+
+// readIgnoreFile reads a specific git ignore file.
+func readIgnoreFile(fs billy.Filesystem, path []string, ignoreFile string) (ps []Pattern, err error) {
+	f, err := fs.Open(fs.Join(append(path, ignoreFile)...))
+	if err == nil {
+		defer f.Close()
+
+		if data, err := ioutil.ReadAll(f); err == nil {
+			for _, s := range strings.Split(string(data), eol) {
+				if !strings.HasPrefix(s, commentPrefix) && len(strings.TrimSpace(s)) > 0 {
+					ps = append(ps, ParsePattern(s, path))
+				}
+			}
+		}
+	} else if !os.IsNotExist(err) {
+		return nil, err
+	}
+
+	return
+}
+
+// ReadPatterns reads gitignore patterns recursively traversing through the directory
+// structure. The result is in the ascending order of priority (last higher).
+func ReadPatterns(fs billy.Filesystem, path []string) (ps []Pattern, err error) {
+	ps, _ = readIgnoreFile(fs, path, gitignoreFile)
+
+	var fis []os.FileInfo
+	fis, err = fs.ReadDir(fs.Join(path...))
+	if err != nil {
+		return
+	}
+
+	for _, fi := range fis {
+		if fi.IsDir() && fi.Name() != gitDir {
+			var subps []Pattern
+			subps, err = ReadPatterns(fs, append(path, fi.Name()))
+			if err != nil {
+				return
+			}
+
+			if len(subps) > 0 {
+				ps = append(ps, subps...)
+			}
+		}
+	}
+
+	return
+}
+
+func loadPatterns(fs billy.Filesystem, path string) (ps []Pattern, err error) {
+	f, err := fs.Open(path)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return nil, nil
+		}
+		return nil, err
+	}
+
+	defer gioutil.CheckClose(f, &err)
+
+	b, err := ioutil.ReadAll(f)
+	if err != nil {
+		return
+	}
+
+	d := config.NewDecoder(bytes.NewBuffer(b))
+
+	raw := config.New()
+	if err = d.Decode(raw); err != nil {
+		return
+	}
+
+	s := raw.Section(coreSection)
+	efo := s.Options.Get(excludesfile)
+	if efo == "" {
+		return nil, nil
+	}
+
+	ps, err = readIgnoreFile(fs, nil, efo)
+	if os.IsNotExist(err) {
+		return nil, nil
+	}
+
+	return
+}
+
+// LoadGlobalPatterns loads gitignore patterns from from the gitignore file
+// declared in a user's ~/.gitconfig file.  If the ~/.gitconfig file does not
+// exist the function will return nil.  If the core.excludesfile property
+// is not declared, the function will return nil.  If the file pointed to by
+// the core.excludesfile property does not exist, the function will return nil.
+//
+// The function assumes fs is rooted at the root filesystem.
+func LoadGlobalPatterns(fs billy.Filesystem) (ps []Pattern, err error) {
+	usr, err := user.Current()
+	if err != nil {
+		return
+	}
+
+	return loadPatterns(fs, fs.Join(usr.HomeDir, gitconfigFile))
+}
+
+// LoadSystemPatterns loads gitignore patterns from from the gitignore file
+// declared in a system's /etc/gitconfig file.  If the ~/.gitconfig file does
+// not exist the function will return nil.  If the core.excludesfile property
+// is not declared, the function will return nil.  If the file pointed to by
+// the core.excludesfile property does not exist, the function will return nil.
+//
+// The function assumes fs is rooted at the root filesystem.
+func LoadSystemPatterns(fs billy.Filesystem) (ps []Pattern, err error) {
+	return loadPatterns(fs, systemFile)
+}

vendor/gopkg.in/src-d/go-git.v4/plumbing/format/gitignore/doc.go

@@ -0,0 +1,70 @@
+// Package gitignore implements matching file system paths to gitignore patterns that
+// can be automatically read from a git repository tree in the order of definition
+// priorities. It support all pattern formats as specified in the original gitignore
+// documentation, copied below:
+//
+//   Pattern format
+//   ==============
+//
+//		- A blank line matches no files, so it can serve as a separator for readability.
+//
+//		- A line starting with # serves as a comment. Put a backslash ("\") in front of
+//		  the first hash for patterns that begin with a hash.
+//
+//		- Trailing spaces are ignored unless they are quoted with backslash ("\").
+//
+//		- An optional prefix "!" which negates the pattern; any matching file excluded
+//		  by a previous pattern will become included again. It is not possible to
+//		  re-include a file if a parent directory of that file is excluded.
+//		  Git doesn’t list excluded directories for performance reasons, so
+//		  any patterns on contained files have no effect, no matter where they are
+//		  defined. Put a backslash ("\") in front of the first "!" for patterns
+//		  that begin with a literal "!", for example, "\!important!.txt".
+//
+//		- If the pattern ends with a slash, it is removed for the purpose of the
+//		  following description, but it would only find a match with a directory.
+//		  In other words, foo/ will match a directory foo and paths underneath it,
+//		  but will not match a regular file or a symbolic link foo (this is consistent
+//		  with the way how pathspec works in general in Git).
+//
+//		- If the pattern does not contain a slash /, Git treats it as a shell glob
+//		  pattern and checks for a match against the pathname relative to the location
+//		  of the .gitignore file (relative to the toplevel of the work tree if not
+//		  from a .gitignore file).
+//
+//		- Otherwise, Git treats the pattern as a shell glob suitable for consumption
+//		  by fnmatch(3) with the FNM_PATHNAME flag: wildcards in the pattern will
+//		  not match a / in the pathname. For example, "Documentation/*.html" matches
+//		  "Documentation/git.html" but not "Documentation/ppc/ppc.html" or
+//		  "tools/perf/Documentation/perf.html".
+//
+//		- A leading slash matches the beginning of the pathname. For example,
+//		  "/*.c" matches "cat-file.c" but not "mozilla-sha1/sha1.c".
+//
+//		Two consecutive asterisks ("**") in patterns matched against full pathname
+//		may have special meaning:
+//
+//		- A leading "**" followed by a slash means match in all directories.
+//		  For example, "**/foo" matches file or directory "foo" anywhere, the same as
+//		  pattern "foo". "**/foo/bar" matches file or directory "bar"
+//		  anywhere that is directly under directory "foo".
+//
+//		- A trailing "/**" matches everything inside. For example, "abc/**" matches
+//		  all files inside directory "abc", relative to the location of the
+//		  .gitignore file, with infinite depth.
+//
+//		- A slash followed by two consecutive asterisks then a slash matches
+//		  zero or more directories. For example, "a/**/b" matches "a/b", "a/x/b",
+//		  "a/x/y/b" and so on.
+//
+//		- Other consecutive asterisks are considered invalid.
+//
+//   Copyright and license
+//   =====================
+//
+//		Copyright (c) Oleg Sklyar, Silvertern and source{d}
+//
+//		The package code was donated to source{d} to include, modify and develop
+//		further as a part of the `go-git` project, release it on the license of
+//		the whole project or delete it from the project.
+package gitignore

vendor/gopkg.in/src-d/go-git.v4/plumbing/format/gitignore/matcher.go

@@ -0,0 +1,30 @@
+package gitignore
+
+// Matcher defines a global multi-pattern matcher for gitignore patterns
+type Matcher interface {
+	// Match matches patterns in the order of priorities. As soon as an inclusion or
+	// exclusion is found, not further matching is performed.
+	Match(path []string, isDir bool) bool
+}
+
+// NewMatcher constructs a new global matcher. Patterns must be given in the order of
+// increasing priority. That is most generic settings files first, then the content of
+// the repo .gitignore, then content of .gitignore down the path or the repo and then
+// the content command line arguments.
+func NewMatcher(ps []Pattern) Matcher {
+	return &matcher{ps}
+}
+
+type matcher struct {
+	patterns []Pattern
+}
+
+func (m *matcher) Match(path []string, isDir bool) bool {
+	n := len(m.patterns)
+	for i := n - 1; i >= 0; i-- {
+		if match := m.patterns[i].Match(path, isDir); match > NoMatch {
+			return match == Exclude
+		}
+	}
+	return false
+}

vendor/gopkg.in/src-d/go-git.v4/plumbing/format/gitignore/pattern.go

@@ -0,0 +1,153 @@
+package gitignore
+
+import (
+	"path/filepath"
+	"strings"
+)
+
+// MatchResult defines outcomes of a match, no match, exclusion or inclusion.
+type MatchResult int
+
+const (
+	// NoMatch defines the no match outcome of a match check
+	NoMatch MatchResult = iota
+	// Exclude defines an exclusion of a file as a result of a match check
+	Exclude
+	// Include defines an explicit inclusion of a file as a result of a match check
+	Include
+)
+
+const (
+	inclusionPrefix = "!"
+	zeroToManyDirs  = "**"
+	patternDirSep   = "/"
+)
+
+// Pattern defines a single gitignore pattern.
+type Pattern interface {
+	// Match matches the given path to the pattern.
+	Match(path []string, isDir bool) MatchResult
+}
+
+type pattern struct {
+	domain    []string
+	pattern   []string
+	inclusion bool
+	dirOnly   bool
+	isGlob    bool
+}
+
+// ParsePattern parses a gitignore pattern string into the Pattern structure.
+func ParsePattern(p string, domain []string) Pattern {
+	res := pattern{domain: domain}
+
+	if strings.HasPrefix(p, inclusionPrefix) {
+		res.inclusion = true
+		p = p[1:]
+	}
+
+	if !strings.HasSuffix(p, "\\ ") {
+		p = strings.TrimRight(p, " ")
+	}
+
+	if strings.HasSuffix(p, patternDirSep) {
+		res.dirOnly = true
+		p = p[:len(p)-1]
+	}
+
+	if strings.Contains(p, patternDirSep) {
+		res.isGlob = true
+	}
+
+	res.pattern = strings.Split(p, patternDirSep)
+	return &res
+}
+
+func (p *pattern) Match(path []string, isDir bool) MatchResult {
+	if len(path) <= len(p.domain) {
+		return NoMatch
+	}
+	for i, e := range p.domain {
+		if path[i] != e {
+			return NoMatch
+		}
+	}
+
+	path = path[len(p.domain):]
+	if p.isGlob && !p.globMatch(path, isDir) {
+		return NoMatch
+	} else if !p.isGlob && !p.simpleNameMatch(path, isDir) {
+		return NoMatch
+	}
+
+	if p.inclusion {
+		return Include
+	} else {
+		return Exclude
+	}
+}
+
+func (p *pattern) simpleNameMatch(path []string, isDir bool) bool {
+	for i, name := range path {
+		if match, err := filepath.Match(p.pattern[0], name); err != nil {
+			return false
+		} else if !match {
+			continue
+		}
+		if p.dirOnly && !isDir && i == len(path)-1 {
+			return false
+		}
+		return true
+	}
+	return false
+}
+
+func (p *pattern) globMatch(path []string, isDir bool) bool {
+	matched := false
+	canTraverse := false
+	for i, pattern := range p.pattern {
+		if pattern == "" {
+			canTraverse = false
+			continue
+		}
+		if pattern == zeroToManyDirs {
+			if i == len(p.pattern)-1 {
+				break
+			}
+			canTraverse = true
+			continue
+		}
+		if strings.Contains(pattern, zeroToManyDirs) {
+			return false
+		}
+		if len(path) == 0 {
+			return false
+		}
+		if canTraverse {
+			canTraverse = false
+			for len(path) > 0 {
+				e := path[0]
+				path = path[1:]
+				if match, err := filepath.Match(pattern, e); err != nil {
+					return false
+				} else if match {
+					matched = true
+					break
+				} else if len(path) == 0 {
+					// if nothing left then fail
+					matched = false
+				}
+			}
+		} else {
+			if match, err := filepath.Match(pattern, path[0]); err != nil || !match {
+				return false
+			}
+			matched = true
+			path = path[1:]
+		}
+	}
+	if matched && p.dirOnly && !isDir && len(path) == 0 {
+		matched = false
+	}
+	return matched
+}

vendor/gopkg.in/src-d/go-git.v4/plumbing/format/idxfile/decoder.go

@@ -0,0 +1,181 @@
+package idxfile
+
+import (
+	"bufio"
+	"bytes"
+	"errors"
+	"io"
+
+	"gopkg.in/src-d/go-git.v4/utils/binary"
+)
+
+var (
+	// ErrUnsupportedVersion is returned by Decode when the idx file version
+	// is not supported.
+	ErrUnsupportedVersion = errors.New("Unsuported version")
+	// ErrMalformedIdxFile is returned by Decode when the idx file is corrupted.
+	ErrMalformedIdxFile = errors.New("Malformed IDX file")
+)
+
+const (
+	fanout         = 256
+	objectIDLength = 20
+)
+
+// Decoder reads and decodes idx files from an input stream.
+type Decoder struct {
+	*bufio.Reader
+}
+
+// NewDecoder builds a new idx stream decoder, that reads from r.
+func NewDecoder(r io.Reader) *Decoder {
+	return &Decoder{bufio.NewReader(r)}
+}
+
+// Decode reads from the stream and decode the content into the MemoryIndex struct.
+func (d *Decoder) Decode(idx *MemoryIndex) error {
+	if err := validateHeader(d); err != nil {
+		return err
+	}
+
+	flow := []func(*MemoryIndex, io.Reader) error{
+		readVersion,
+		readFanout,
+		readObjectNames,
+		readCRC32,
+		readOffsets,
+		readChecksums,
+	}
+
+	for _, f := range flow {
+		if err := f(idx, d); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func validateHeader(r io.Reader) error {
+	var h = make([]byte, 4)
+	if _, err := io.ReadFull(r, h); err != nil {
+		return err
+	}
+
+	if !bytes.Equal(h, idxHeader) {
+		return ErrMalformedIdxFile
+	}
+
+	return nil
+}
+
+func readVersion(idx *MemoryIndex, r io.Reader) error {
+	v, err := binary.ReadUint32(r)
+	if err != nil {
+		return err
+	}
+
+	if v > VersionSupported {
+		return ErrUnsupportedVersion
+	}
+
+	idx.Version = v
+	return nil
+}
+
+func readFanout(idx *MemoryIndex, r io.Reader) error {
+	for k := 0; k < fanout; k++ {
+		n, err := binary.ReadUint32(r)
+		if err != nil {
+			return err
+		}
+
+		idx.Fanout[k] = n
+		idx.FanoutMapping[k] = noMapping
+	}
+
+	return nil
+}
+
+func readObjectNames(idx *MemoryIndex, r io.Reader) error {
+	for k := 0; k < fanout; k++ {
+		var buckets uint32
+		if k == 0 {
+			buckets = idx.Fanout[k]
+		} else {
+			buckets = idx.Fanout[k] - idx.Fanout[k-1]
+		}
+
+		if buckets == 0 {
+			continue
+		}
+
+		if buckets < 0 {
+			return ErrMalformedIdxFile
+		}
+
+		idx.FanoutMapping[k] = len(idx.Names)
+
+		nameLen := int(buckets * objectIDLength)
+		bin := make([]byte, nameLen)
+		if _, err := io.ReadFull(r, bin); err != nil {
+			return err
+		}
+
+		idx.Names = append(idx.Names, bin)
+		idx.Offset32 = append(idx.Offset32, make([]byte, buckets*4))
+		idx.CRC32 = append(idx.CRC32, make([]byte, buckets*4))
+	}
+
+	return nil
+}
+
+func readCRC32(idx *MemoryIndex, r io.Reader) error {
+	for k := 0; k < fanout; k++ {
+		if pos := idx.FanoutMapping[k]; pos != noMapping {
+			if _, err := io.ReadFull(r, idx.CRC32[pos]); err != nil {
+				return err
+			}
+		}
+	}
+
+	return nil
+}
+
+func readOffsets(idx *MemoryIndex, r io.Reader) error {
+	var o64cnt int
+	for k := 0; k < fanout; k++ {
+		if pos := idx.FanoutMapping[k]; pos != noMapping {
+			if _, err := io.ReadFull(r, idx.Offset32[pos]); err != nil {
+				return err
+			}
+
+			for p := 0; p < len(idx.Offset32[pos]); p += 4 {
+				if idx.Offset32[pos][p]&(byte(1)<<7) > 0 {
+					o64cnt++
+				}
+			}
+		}
+	}
+
+	if o64cnt > 0 {
+		idx.Offset64 = make([]byte, o64cnt*8)
+		if _, err := io.ReadFull(r, idx.Offset64); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func readChecksums(idx *MemoryIndex, r io.Reader) error {
+	if _, err := io.ReadFull(r, idx.PackfileChecksum[:]); err != nil {
+		return err
+	}
+
+	if _, err := io.ReadFull(r, idx.IdxChecksum[:]); err != nil {
+		return err
+	}
+
+	return nil
+}

vendor/gopkg.in/src-d/go-git.v4/plumbing/format/idxfile/doc.go

@@ -0,0 +1,128 @@
+// Package idxfile implements encoding and decoding of packfile idx files.
+//
+//  == Original (version 1) pack-*.idx files have the following format:
+//
+//    - The header consists of 256 4-byte network byte order
+//      integers.  N-th entry of this table records the number of
+//      objects in the corresponding pack, the first byte of whose
+//      object name is less than or equal to N.  This is called the
+//      'first-level fan-out' table.
+//
+//    - The header is followed by sorted 24-byte entries, one entry
+//      per object in the pack.  Each entry is:
+//
+//     4-byte network byte order integer, recording where the
+//     object is stored in the packfile as the offset from the
+//     beginning.
+//
+//     20-byte object name.
+//
+//   - The file is concluded with a trailer:
+//
+//     A copy of the 20-byte SHA1 checksum at the end of
+//     corresponding packfile.
+//
+//     20-byte SHA1-checksum of all of the above.
+//
+//   Pack Idx file:
+//
+//        --  +--------------------------------+
+//   fanout   | fanout[0] = 2 (for example)    |-.
+//   table    +--------------------------------+ |
+//            | fanout[1]                      | |
+//            +--------------------------------+ |
+//            | fanout[2]                      | |
+//            ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |
+//            | fanout[255] = total objects    |---.
+//        --  +--------------------------------+ | |
+//   main     | offset                         | | |
+//   index    | object name 00XXXXXXXXXXXXXXXX | | |
+//   tab      +--------------------------------+ | |
+//            | offset                         | | |
+//            | object name 00XXXXXXXXXXXXXXXX | | |
+//            +--------------------------------+<+ |
+//          .-| offset                         |   |
+//          | | object name 01XXXXXXXXXXXXXXXX |   |
+//          | +--------------------------------+   |
+//          | | offset                         |   |
+//          | | object name 01XXXXXXXXXXXXXXXX |   |
+//          | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~   |
+//          | | offset                         |   |
+//          | | object name FFXXXXXXXXXXXXXXXX |   |
+//        --| +--------------------------------+<--+
+//  trailer | | packfile checksum              |
+//          | +--------------------------------+
+//          | | idxfile checksum               |
+//          | +--------------------------------+
+//          .---------.
+//                    |
+//  Pack file entry: <+
+//
+//     packed object header:
+//     1-byte size extension bit (MSB)
+//           type (next 3 bit)
+//           size0 (lower 4-bit)
+//         n-byte sizeN (as long as MSB is set, each 7-bit)
+//         size0..sizeN form 4+7+7+..+7 bit integer, size0
+//         is the least significant part, and sizeN is the
+//         most significant part.
+//     packed object data:
+//         If it is not DELTA, then deflated bytes (the size above
+//         is the size before compression).
+//     If it is REF_DELTA, then
+//       20-byte base object name SHA1 (the size above is the
+//         size of the delta data that follows).
+//           delta data, deflated.
+//     If it is OFS_DELTA, then
+//       n-byte offset (see below) interpreted as a negative
+//         offset from the type-byte of the header of the
+//         ofs-delta entry (the size above is the size of
+//         the delta data that follows).
+//       delta data, deflated.
+//
+//     offset encoding:
+//       n bytes with MSB set in all but the last one.
+//       The offset is then the number constructed by
+//       concatenating the lower 7 bit of each byte, and
+//       for n >= 2 adding 2^7 + 2^14 + ... + 2^(7*(n-1))
+//       to the result.
+//
+//   == Version 2 pack-*.idx files support packs larger than 4 GiB, and
+//      have some other reorganizations.  They have the format:
+//
+//     - A 4-byte magic number '\377tOc' which is an unreasonable
+//       fanout[0] value.
+//
+//     - A 4-byte version number (= 2)
+//
+//     - A 256-entry fan-out table just like v1.
+//
+//     - A table of sorted 20-byte SHA1 object names.  These are
+//       packed together without offset values to reduce the cache
+//       footprint of the binary search for a specific object name.
+//
+//     - A table of 4-byte CRC32 values of the packed object data.
+//       This is new in v2 so compressed data can be copied directly
+//       from pack to pack during repacking without undetected
+//       data corruption.
+//
+//     - A table of 4-byte offset values (in network byte order).
+//       These are usually 31-bit pack file offsets, but large
+//       offsets are encoded as an index into the next table with
+//       the msbit set.
+//
+//     - A table of 8-byte offset entries (empty for pack files less
+//       than 2 GiB).  Pack files are organized with heavily used
+//       objects toward the front, so most object references should
+//       not need to refer to this table.
+//
+//     - The same trailer as a v1 pack file:
+//
+//       A copy of the 20-byte SHA1 checksum at the end of
+//       corresponding packfile.
+//
+//       20-byte SHA1-checksum of all of the above.
+//
+// Source:
+// https://www.kernel.org/pub/software/scm/git/docs/v1.7.5/technical/pack-format.txt
+package idxfile

vendor/gopkg.in/src-d/go-git.v4/plumbing/format/idxfile/encoder.go

@@ -0,0 +1,142 @@
+package idxfile
+
+import (
+	"crypto/sha1"
+	"hash"
+	"io"
+
+	"gopkg.in/src-d/go-git.v4/utils/binary"
+)
+
+// Encoder writes MemoryIndex structs to an output stream.
+type Encoder struct {
+	io.Writer
+	hash hash.Hash
+}
+
+// NewEncoder returns a new stream encoder that writes to w.
+func NewEncoder(w io.Writer) *Encoder {
+	h := sha1.New()
+	mw := io.MultiWriter(w, h)
+	return &Encoder{mw, h}
+}
+
+// Encode encodes an MemoryIndex to the encoder writer.
+func (e *Encoder) Encode(idx *MemoryIndex) (int, error) {
+	flow := []func(*MemoryIndex) (int, error){
+		e.encodeHeader,
+		e.encodeFanout,
+		e.encodeHashes,
+		e.encodeCRC32,
+		e.encodeOffsets,
+		e.encodeChecksums,
+	}
+
+	sz := 0
+	for _, f := range flow {
+		i, err := f(idx)
+		sz += i
+
+		if err != nil {
+			return sz, err
+		}
+	}
+
+	return sz, nil
+}
+
+func (e *Encoder) encodeHeader(idx *MemoryIndex) (int, error) {
+	c, err := e.Write(idxHeader)
+	if err != nil {
+		return c, err
+	}
+
+	return c + 4, binary.WriteUint32(e, idx.Version)
+}
+
+func (e *Encoder) encodeFanout(idx *MemoryIndex) (int, error) {
+	for _, c := range idx.Fanout {
+		if err := binary.WriteUint32(e, c); err != nil {
+			return 0, err
+		}
+	}
+
+	return fanout * 4, nil
+}
+
+func (e *Encoder) encodeHashes(idx *MemoryIndex) (int, error) {
+	var size int
+	for k := 0; k < fanout; k++ {
+		pos := idx.FanoutMapping[k]
+		if pos == noMapping {
+			continue
+		}
+
+		n, err := e.Write(idx.Names[pos])
+		if err != nil {
+			return size, err
+		}
+		size += n
+	}
+	return size, nil
+}
+
+func (e *Encoder) encodeCRC32(idx *MemoryIndex) (int, error) {
+	var size int
+	for k := 0; k < fanout; k++ {
+		pos := idx.FanoutMapping[k]
+		if pos == noMapping {
+			continue
+		}
+
+		n, err := e.Write(idx.CRC32[pos])
+		if err != nil {
+			return size, err
+		}
+
+		size += n
+	}
+
+	return size, nil
+}
+
+func (e *Encoder) encodeOffsets(idx *MemoryIndex) (int, error) {
+	var size int
+	for k := 0; k < fanout; k++ {
+		pos := idx.FanoutMapping[k]
+		if pos == noMapping {
+			continue
+		}
+
+		n, err := e.Write(idx.Offset32[pos])
+		if err != nil {
+			return size, err
+		}
+
+		size += n
+	}
+
+	if len(idx.Offset64) > 0 {
+		n, err := e.Write(idx.Offset64)
+		if err != nil {
+			return size, err
+		}
+
+		size += n
+	}
+
+	return size, nil
+}
+
+func (e *Encoder) encodeChecksums(idx *MemoryIndex) (int, error) {
+	if _, err := e.Write(idx.PackfileChecksum[:]); err != nil {
+		return 0, err
+	}
+
+	copy(idx.IdxChecksum[:], e.hash.Sum(nil)[:20])
+	if _, err := e.Write(idx.IdxChecksum[:]); err != nil {
+		return 0, err
+	}
+
+	return 40, nil
+}

vendor/gopkg.in/src-d/go-git.v4/plumbing/format/idxfile/idxfile.go

@@ -0,0 +1,347 @@
+package idxfile
+
+import (
+	"bytes"
+	"io"
+	"sort"
+
+	"gopkg.in/src-d/go-git.v4/plumbing"
+	"gopkg.in/src-d/go-git.v4/utils/binary"
+)
+
+const (
+	// VersionSupported is the only idx version supported.
+	VersionSupported = 2
+
+	noMapping = -1
+)
+
+var (
+	idxHeader = []byte{255, 't', 'O', 'c'}
+)
+
+// Index represents an index of a packfile.
+type Index interface {
+	// Contains checks whether the given hash is in the index.
+	Contains(h plumbing.Hash) (bool, error)
+	// FindOffset finds the offset in the packfile for the object with
+	// the given hash.
+	FindOffset(h plumbing.Hash) (int64, error)
+	// FindCRC32 finds the CRC32 of the object with the given hash.
+	FindCRC32(h plumbing.Hash) (uint32, error)
+	// FindHash finds the hash for the object with the given offset.
+	FindHash(o int64) (plumbing.Hash, error)
+	// Count returns the number of entries in the index.
+	Count() (int64, error)
+	// Entries returns an iterator to retrieve all index entries.
+	Entries() (EntryIter, error)
+	// EntriesByOffset returns an iterator to retrieve all index entries ordered
+	// by offset.
+	EntriesByOffset() (EntryIter, error)
+}
+
+// MemoryIndex is the in memory representation of an idx file.
+type MemoryIndex struct {
+	Version uint32
+	Fanout  [256]uint32
+	// FanoutMapping maps the position in the fanout table to the position
+	// in the Names, Offset32 and CRC32 slices. This improves the memory
+	// usage by not needing an array with unnecessary empty slots.
+	FanoutMapping    [256]int
+	Names            [][]byte
+	Offset32         [][]byte
+	CRC32            [][]byte
+	Offset64         []byte
+	PackfileChecksum [20]byte
+	IdxChecksum      [20]byte
+
+	offsetHash map[int64]plumbing.Hash
+}
+
+var _ Index = (*MemoryIndex)(nil)
+
+// NewMemoryIndex returns an instance of a new MemoryIndex.
+func NewMemoryIndex() *MemoryIndex {
+	return &MemoryIndex{}
+}
+
+func (idx *MemoryIndex) findHashIndex(h plumbing.Hash) (int, bool) {
+	k := idx.FanoutMapping[h[0]]
+	if k == noMapping {
+		return 0, false
+	}
+
+	if len(idx.Names) <= k {
+		return 0, false
+	}
+
+	data := idx.Names[k]
+	high := uint64(len(idx.Offset32[k])) >> 2
+	if high == 0 {
+		return 0, false
+	}
+
+	low := uint64(0)
+	for {
+		mid := (low + high) >> 1
+		offset := mid * objectIDLength
+
+		cmp := bytes.Compare(h[:], data[offset:offset+objectIDLength])
+		if cmp < 0 {
+			high = mid
+		} else if cmp == 0 {
+			return int(mid), true
+		} else {
+			low = mid + 1
+		}
+
+		if low >= high {
+			break
+		}
+	}
+
+	return 0, false
+}
+
+// Contains implements the Index interface.
+func (idx *MemoryIndex) Contains(h plumbing.Hash) (bool, error) {
+	_, ok := idx.findHashIndex(h)
+	return ok, nil
+}
+
+// FindOffset implements the Index interface.
+func (idx *MemoryIndex) FindOffset(h plumbing.Hash) (int64, error) {
+	if len(idx.FanoutMapping) <= int(h[0]) {
+		return 0, plumbing.ErrObjectNotFound
+	}
+
+	k := idx.FanoutMapping[h[0]]
+	i, ok := idx.findHashIndex(h)
+	if !ok {
+		return 0, plumbing.ErrObjectNotFound
+	}
+
+	return idx.getOffset(k, i)
+}
+
+const isO64Mask = uint64(1) << 31
+
+func (idx *MemoryIndex) getOffset(firstLevel, secondLevel int) (int64, error) {
+	offset := secondLevel << 2
+	buf := bytes.NewBuffer(idx.Offset32[firstLevel][offset : offset+4])
+	ofs, err := binary.ReadUint32(buf)
+	if err != nil {
+		return -1, err
+	}
+
+	if (uint64(ofs) & isO64Mask) != 0 {
+		offset := 8 * (uint64(ofs) & ^isO64Mask)
+		buf := bytes.NewBuffer(idx.Offset64[offset : offset+8])
+		n, err := binary.ReadUint64(buf)
+		if err != nil {
+			return -1, err
+		}
+
+		return int64(n), nil
+	}
+
+	return int64(ofs), nil
+}
+
+// FindCRC32 implements the Index interface.
+func (idx *MemoryIndex) FindCRC32(h plumbing.Hash) (uint32, error) {
+	k := idx.FanoutMapping[h[0]]
+	i, ok := idx.findHashIndex(h)
+	if !ok {
+		return 0, plumbing.ErrObjectNotFound
+	}
+
+	return idx.getCRC32(k, i)
+}
+
+func (idx *MemoryIndex) getCRC32(firstLevel, secondLevel int) (uint32, error) {
+	offset := secondLevel << 2
+	buf := bytes.NewBuffer(idx.CRC32[firstLevel][offset : offset+4])
+	return binary.ReadUint32(buf)
+}
+
+// FindHash implements the Index interface.
+func (idx *MemoryIndex) FindHash(o int64) (plumbing.Hash, error) {
+	// Lazily generate the reverse offset/hash map if required.
+	if idx.offsetHash == nil {
+		if err := idx.genOffsetHash(); err != nil {
+			return plumbing.ZeroHash, err
+		}
+	}
+
+	hash, ok := idx.offsetHash[o]
+	if !ok {
+		return plumbing.ZeroHash, plumbing.ErrObjectNotFound
+	}
+
+	return hash, nil
+}
+
+// genOffsetHash generates the offset/hash mapping for reverse search.
+func (idx *MemoryIndex) genOffsetHash() error {
+	count, err := idx.Count()
+	if err != nil {
+		return err
+	}
+
+	idx.offsetHash = make(map[int64]plumbing.Hash, count)
+
+	iter, err := idx.Entries()
+	if err != nil {
+		return err
+	}
+
+	for {
+		entry, err := iter.Next()
+		if err != nil {
+			if err == io.EOF {
+				return nil
+			}
+			return err
+		}
+
+		idx.offsetHash[int64(entry.Offset)] = entry.Hash
+	}
+}
+
+// Count implements the Index interface.
+func (idx *MemoryIndex) Count() (int64, error) {
+	return int64(idx.Fanout[fanout-1]), nil
+}
+
+// Entries implements the Index interface.
+func (idx *MemoryIndex) Entries() (EntryIter, error) {
+	return &idxfileEntryIter{idx, 0, 0, 0}, nil
+}
+
+// EntriesByOffset implements the Index interface.
+func (idx *MemoryIndex) EntriesByOffset() (EntryIter, error) {
+	count, err := idx.Count()
+	if err != nil {
+		return nil, err
+	}
+
+	iter := &idxfileEntryOffsetIter{
+		entries: make(entriesByOffset, count),
+	}
+
+	entries, err := idx.Entries()
+	if err != nil {
+		return nil, err
+	}
+
+	for pos := 0; int64(pos) < count; pos++ {
+		entry, err := entries.Next()
+		if err != nil {
+			return nil, err
+		}
+
+		iter.entries[pos] = entry
+	}
+
+	sort.Sort(iter.entries)
+
+	return iter, nil
+}
+
+// EntryIter is an iterator that will return the entries in a packfile index.
+type EntryIter interface {
+	// Next returns the next entry in the packfile index.
+	Next() (*Entry, error)
+	// Close closes the iterator.
+	Close() error
+}
+
+type idxfileEntryIter struct {
+	idx                     *MemoryIndex
+	total                   int
+	firstLevel, secondLevel int
+}
+
+func (i *idxfileEntryIter) Next() (*Entry, error) {
+	for {
+		if i.firstLevel >= fanout {
+			return nil, io.EOF
+		}
+
+		if i.total >= int(i.idx.Fanout[i.firstLevel]) {
+			i.firstLevel++
+			i.secondLevel = 0
+			continue
+		}
+
+		entry := new(Entry)
+		ofs := i.secondLevel * objectIDLength
+		copy(entry.Hash[:], i.idx.Names[i.idx.FanoutMapping[i.firstLevel]][ofs:])
+
+		pos := i.idx.FanoutMapping[entry.Hash[0]]
+
+		offset, err := i.idx.getOffset(pos, i.secondLevel)
+		if err != nil {
+			return nil, err
+		}
+		entry.Offset = uint64(offset)
+
+		entry.CRC32, err = i.idx.getCRC32(pos, i.secondLevel)
+		if err != nil {
+			return nil, err
+		}
+
+		i.secondLevel++
+		i.total++
+
+		return entry, nil
+	}
+}
+
+func (i *idxfileEntryIter) Close() error {
+	i.firstLevel = fanout
+	return nil
+}
+
+// Entry is the in memory representation of an object entry in the idx file.
+type Entry struct {
+	Hash   plumbing.Hash
+	CRC32  uint32
+	Offset uint64
+}
+
+type idxfileEntryOffsetIter struct {
+	entries entriesByOffset
+	pos     int
+}
+
+func (i *idxfileEntryOffsetIter) Next() (*Entry, error) {
+	if i.pos >= len(i.entries) {
+		return nil, io.EOF
+	}
+
+	entry := i.entries[i.pos]
+	i.pos++
+
+	return entry, nil
+}
+
+func (i *idxfileEntryOffsetIter) Close() error {
+	i.pos = len(i.entries) + 1
+	return nil
+}
+
+type entriesByOffset []*Entry
+
+func (o entriesByOffset) Len() int {
+	return len(o)
+}
+
+func (o entriesByOffset) Less(i int, j int) bool {
+	return o[i].Offset < o[j].Offset
+}
+
+func (o entriesByOffset) Swap(i int, j int) {
+	o[i], o[j] = o[j], o[i]
+}

vendor/gopkg.in/src-d/go-git.v4/plumbing/format/idxfile/writer.go

@@ -0,0 +1,186 @@
+package idxfile
+
+import (
+	"bytes"
+	"fmt"
+	"math"
+	"sort"
+	"sync"
+
+	"gopkg.in/src-d/go-git.v4/plumbing"
+	"gopkg.in/src-d/go-git.v4/utils/binary"
+)
+
+// objects implements sort.Interface and uses hash as sorting key.
+type objects []Entry
+
+// Writer implements a packfile Observer interface and is used to generate
+// indexes.
+type Writer struct {
+	m sync.Mutex
+
+	count    uint32
+	checksum plumbing.Hash
+	objects  objects
+	offset64 uint32
+	finished bool
+	index    *MemoryIndex
+	added    map[plumbing.Hash]struct{}
+}
+
+// Index returns a previously created MemoryIndex or creates a new one if
+// needed.
+func (w *Writer) Index() (*MemoryIndex, error) {
+	w.m.Lock()
+	defer w.m.Unlock()
+
+	if w.index == nil {
+		return w.createIndex()
+	}
+
+	return w.index, nil
+}
+
+// Add appends new object data.
+func (w *Writer) Add(h plumbing.Hash, pos uint64, crc uint32) {
+	w.m.Lock()
+	defer w.m.Unlock()
+
+	if w.added == nil {
+		w.added = make(map[plumbing.Hash]struct{})
+	}
+
+	if _, ok := w.added[h]; !ok {
+		w.added[h] = struct{}{}
+		w.objects = append(w.objects, Entry{h, crc, pos})
+	}
+
+}
+
+func (w *Writer) Finished() bool {
+	return w.finished
+}
+
+// OnHeader implements packfile.Observer interface.
+func (w *Writer) OnHeader(count uint32) error {
+	w.count = count
+	w.objects = make(objects, 0, count)
+	return nil
+}
+
+// OnInflatedObjectHeader implements packfile.Observer interface.
+func (w *Writer) OnInflatedObjectHeader(t plumbing.ObjectType, objSize int64, pos int64) error {
+	return nil
+}
+
+// OnInflatedObjectContent implements packfile.Observer interface.
+func (w *Writer) OnInflatedObjectContent(h plumbing.Hash, pos int64, crc uint32, _ []byte) error {
+	w.Add(h, uint64(pos), crc)
+	return nil
+}
+
+// OnFooter implements packfile.Observer interface.
+func (w *Writer) OnFooter(h plumbing.Hash) error {
+	w.checksum = h
+	w.finished = true
+	_, err := w.createIndex()
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+// creatIndex returns a filled MemoryIndex with the information filled by
+// the observer callbacks.
+func (w *Writer) createIndex() (*MemoryIndex, error) {
+	if !w.finished {
+		return nil, fmt.Errorf("the index still hasn't finished building")
+	}
+
+	idx := new(MemoryIndex)
+	w.index = idx
+
+	sort.Sort(w.objects)
+
+	// unmap all fans by default
+	for i := range idx.FanoutMapping {
+		idx.FanoutMapping[i] = noMapping
+	}
+
+	buf := new(bytes.Buffer)
+
+	last := -1
+	bucket := -1
+	for i, o := range w.objects {
+		fan := o.Hash[0]
+
+		// fill the gaps between fans
+		for j := last + 1; j < int(fan); j++ {
+			idx.Fanout[j] = uint32(i)
+		}
+
+		// update the number of objects for this position
+		idx.Fanout[fan] = uint32(i + 1)
+
+		// we move from one bucket to another, update counters and allocate
+		// memory
+		if last != int(fan) {
+			bucket++
+			idx.FanoutMapping[fan] = bucket
+			last = int(fan)
+
+			idx.Names = append(idx.Names, make([]byte, 0))
+			idx.Offset32 = append(idx.Offset32, make([]byte, 0))
+			idx.CRC32 = append(idx.CRC32, make([]byte, 0))
+		}
+
+		idx.Names[bucket] = append(idx.Names[bucket], o.Hash[:]...)
+
+		offset := o.Offset
+		if offset > math.MaxInt32 {
+			offset = w.addOffset64(offset)
+		}
+
+		buf.Truncate(0)
+		binary.WriteUint32(buf, uint32(offset))
+		idx.Offset32[bucket] = append(idx.Offset32[bucket], buf.Bytes()...)
+
+		buf.Truncate(0)
+		binary.WriteUint32(buf, uint32(o.CRC32))
+		idx.CRC32[bucket] = append(idx.CRC32[bucket], buf.Bytes()...)
+	}
+
+	for j := last + 1; j < 256; j++ {
+		idx.Fanout[j] = uint32(len(w.objects))
+	}
+
+	idx.Version = VersionSupported
+	idx.PackfileChecksum = w.checksum
+
+	return idx, nil
+}
+
+func (w *Writer) addOffset64(pos uint64) uint64 {
+	buf := new(bytes.Buffer)
+	binary.WriteUint64(buf, pos)
+	w.index.Offset64 = append(w.index.Offset64, buf.Bytes()...)
+
+	index := uint64(w.offset64 | (1 << 31))
+	w.offset64++
+
+	return index
+}
+
+func (o objects) Len() int {
+	return len(o)
+}
+
+func (o objects) Less(i int, j int) bool {
+	cmp := bytes.Compare(o[i].Hash[:], o[j].Hash[:])
+	return cmp < 0
+}
+
+func (o objects) Swap(i int, j int) {
+	o[i], o[j] = o[j], o[i]
+}

vendor/gopkg.in/src-d/go-git.v4/plumbing/format/index/decoder.go

@@ -0,0 +1,476 @@
+package index
+
+import (
+	"bytes"
+	"crypto/sha1"
+	"errors"
+	"hash"
+	"io"
+	"io/ioutil"
+	"strconv"
+	"time"
+
+	"gopkg.in/src-d/go-git.v4/plumbing"
+	"gopkg.in/src-d/go-git.v4/utils/binary"
+)
+
+var (
+	// DecodeVersionSupported is the range of supported index versions
+	DecodeVersionSupported = struct{ Min, Max uint32 }{Min: 2, Max: 4}
+
+	// ErrMalformedSignature is returned by Decode when the index header file is
+	// malformed
+	ErrMalformedSignature = errors.New("malformed index signature file")
+	// ErrInvalidChecksum is returned by Decode if the SHA1 hash mismatch with
+	// the read content
+	ErrInvalidChecksum = errors.New("invalid checksum")
+
+	errUnknownExtension = errors.New("unknown extension")
+)
+
+const (
+	entryHeaderLength = 62
+	entryExtended     = 0x4000
+	entryValid        = 0x8000
+	nameMask          = 0xfff
+	intentToAddMask   = 1 << 13
+	skipWorkTreeMask  = 1 << 14
+)
+
+// A Decoder reads and decodes index files from an input stream.
+type Decoder struct {
+	r         io.Reader
+	hash      hash.Hash
+	lastEntry *Entry
+}
+
+// NewDecoder returns a new decoder that reads from r.
+func NewDecoder(r io.Reader) *Decoder {
+	h := sha1.New()
+	return &Decoder{
+		r:    io.TeeReader(r, h),
+		hash: h,
+	}
+}
+
+// Decode reads the whole index object from its input and stores it in the
+// value pointed to by idx.
+func (d *Decoder) Decode(idx *Index) error {
+	var err error
+	idx.Version, err = validateHeader(d.r)
+	if err != nil {
+		return err
+	}
+
+	entryCount, err := binary.ReadUint32(d.r)
+	if err != nil {
+		return err
+	}
+
+	if err := d.readEntries(idx, int(entryCount)); err != nil {
+		return err
+	}
+
+	return d.readExtensions(idx)
+}
+
+func (d *Decoder) readEntries(idx *Index, count int) error {
+	for i := 0; i < count; i++ {
+		e, err := d.readEntry(idx)
+		if err != nil {
+			return err
+		}
+
+		d.lastEntry = e
+		idx.Entries = append(idx.Entries, e)
+	}
+
+	return nil
+}
+
+func (d *Decoder) readEntry(idx *Index) (*Entry, error) {
+	e := &Entry{}
+
+	var msec, mnsec, sec, nsec uint32
+	var flags uint16
+
+	flow := []interface{}{
+		&sec, &nsec,
+		&msec, &mnsec,
+		&e.Dev,
+		&e.Inode,
+		&e.Mode,
+		&e.UID,
+		&e.GID,
+		&e.Size,
+		&e.Hash,
+		&flags,
+	}
+
+	if err := binary.Read(d.r, flow...); err != nil {
+		return nil, err
+	}
+
+	read := entryHeaderLength
+
+	if sec != 0 || nsec != 0 {
+		e.CreatedAt = time.Unix(int64(sec), int64(nsec))
+	}
+
+	if msec != 0 || mnsec != 0 {
+		e.ModifiedAt = time.Unix(int64(msec), int64(mnsec))
+	}
+
+	e.Stage = Stage(flags>>12) & 0x3
+
+	if flags&entryExtended != 0 {
+		extended, err := binary.ReadUint16(d.r)
+		if err != nil {
+			return nil, err
+		}
+
+		read += 2
+		e.IntentToAdd = extended&intentToAddMask != 0
+		e.SkipWorktree = extended&skipWorkTreeMask != 0
+	}
+
+	if err := d.readEntryName(idx, e, flags); err != nil {
+		return nil, err
+	}
+
+	return e, d.padEntry(idx, e, read)
+}
+
+func (d *Decoder) readEntryName(idx *Index, e *Entry, flags uint16) error {
+	var name string
+	var err error
+
+	switch idx.Version {
+	case 2, 3:
+		len := flags & nameMask
+		name, err = d.doReadEntryName(len)
+	case 4:
+		name, err = d.doReadEntryNameV4()
+	default:
+		return ErrUnsupportedVersion
+	}
+
+	if err != nil {
+		return err
+	}
+
+	e.Name = name
+	return nil
+}
+
+func (d *Decoder) doReadEntryNameV4() (string, error) {
+	l, err := binary.ReadVariableWidthInt(d.r)
+	if err != nil {
+		return "", err
+	}
+
+	var base string
+	if d.lastEntry != nil {
+		base = d.lastEntry.Name[:len(d.lastEntry.Name)-int(l)]
+	}
+
+	name, err := binary.ReadUntil(d.r, '\x00')
+	if err != nil {
+		return "", err
+	}
+
+	return base + string(name), nil
+}
+
+func (d *Decoder) doReadEntryName(len uint16) (string, error) {
+	name := make([]byte, len)
+	if err := binary.Read(d.r, &name); err != nil {
+		return "", err
+	}
+
+	return string(name), nil
+}
+
+// Index entries are padded out to the next 8 byte alignment
+// for historical reasons related to how C Git read the files.
+func (d *Decoder) padEntry(idx *Index, e *Entry, read int) error {
+	if idx.Version == 4 {
+		return nil
+	}
+
+	entrySize := read + len(e.Name)
+	padLen := 8 - entrySize%8
+	_, err := io.CopyN(ioutil.Discard, d.r, int64(padLen))
+	return err
+}
+
+func (d *Decoder) readExtensions(idx *Index) error {
+	// TODO: support 'Split index' and 'Untracked cache' extensions, take in
+	// count that they are not supported by jgit or libgit
+
+	var expected []byte
+	var err error
+
+	var header [4]byte
+	for {
+		expected = d.hash.Sum(nil)
+
+		var n int
+		if n, err = io.ReadFull(d.r, header[:]); err != nil {
+			if n == 0 {
+				err = io.EOF
+			}
+
+			break
+		}
+
+		err = d.readExtension(idx, header[:])
+		if err != nil {
+			break
+		}
+	}
+
+	if err != errUnknownExtension {
+		return err
+	}
+
+	return d.readChecksum(expected, header)
+}
+
+func (d *Decoder) readExtension(idx *Index, header []byte) error {
+	switch {
+	case bytes.Equal(header, treeExtSignature):
+		r, err := d.getExtensionReader()
+		if err != nil {
+			return err
+		}
+
+		idx.Cache = &Tree{}
+		d := &treeExtensionDecoder{r}
+		if err := d.Decode(idx.Cache); err != nil {
+			return err
+		}
+	case bytes.Equal(header, resolveUndoExtSignature):
+		r, err := d.getExtensionReader()
+		if err != nil {
+			return err
+		}
+
+		idx.ResolveUndo = &ResolveUndo{}
+		d := &resolveUndoDecoder{r}
+		if err := d.Decode(idx.ResolveUndo); err != nil {
+			return err
+		}
+	case bytes.Equal(header, endOfIndexEntryExtSignature):
+		r, err := d.getExtensionReader()
+		if err != nil {
+			return err
+		}
+
+		idx.EndOfIndexEntry = &EndOfIndexEntry{}
+		d := &endOfIndexEntryDecoder{r}
+		if err := d.Decode(idx.EndOfIndexEntry); err != nil {
+			return err
+		}
+	default:
+		return errUnknownExtension
+	}
+
+	return nil
+}
+
+func (d *Decoder) getExtensionReader() (io.Reader, error) {
+	len, err := binary.ReadUint32(d.r)
+	if err != nil {
+		return nil, err
+	}
+
+	return &io.LimitedReader{R: d.r, N: int64(len)}, nil
+}
+
+func (d *Decoder) readChecksum(expected []byte, alreadyRead [4]byte) error {
+	var h plumbing.Hash
+	copy(h[:4], alreadyRead[:])
+
+	if err := binary.Read(d.r, h[4:]); err != nil {
+		return err
+	}
+
+	if !bytes.Equal(h[:], expected) {
+		return ErrInvalidChecksum
+	}
+
+	return nil
+}
+
+func validateHeader(r io.Reader) (version uint32, err error) {
+	var s = make([]byte, 4)
+	if _, err := io.ReadFull(r, s); err != nil {
+		return 0, err
+	}
+
+	if !bytes.Equal(s, indexSignature) {
+		return 0, ErrMalformedSignature
+	}
+
+	version, err = binary.ReadUint32(r)
+	if err != nil {
+		return 0, err
+	}
+
+	if version < DecodeVersionSupported.Min || version > DecodeVersionSupported.Max {
+		return 0, ErrUnsupportedVersion
+	}
+
+	return
+}
+
+type treeExtensionDecoder struct {
+	r io.Reader
+}
+
+func (d *treeExtensionDecoder) Decode(t *Tree) error {
+	for {
+		e, err := d.readEntry()
+		if err != nil {
+			if err == io.EOF {
+				return nil
+			}
+
+			return err
+		}
+
+		if e == nil {
+			continue
+		}
+
+		t.Entries = append(t.Entries, *e)
+	}
+}
+
+func (d *treeExtensionDecoder) readEntry() (*TreeEntry, error) {
+	e := &TreeEntry{}
+
+	path, err := binary.ReadUntil(d.r, '\x00')
+	if err != nil {
+		return nil, err
+	}
+
+	e.Path = string(path)
+
+	count, err := binary.ReadUntil(d.r, ' ')
+	if err != nil {
+		return nil, err
+	}
+
+	i, err := strconv.Atoi(string(count))
+	if err != nil {
+		return nil, err
+	}
+
+	// An entry can be in an invalidated state and is represented by having a
+	// negative number in the entry_count field.
+	if i == -1 {
+		return nil, nil
+	}
+
+	e.Entries = i
+	trees, err := binary.ReadUntil(d.r, '\n')
+	if err != nil {
+		return nil, err
+	}
+
+	i, err = strconv.Atoi(string(trees))
+	if err != nil {
+		return nil, err
+	}
+
+	e.Trees = i
+
+	if err := binary.Read(d.r, &e.Hash); err != nil {
+		return nil, err
+	}
+
+	return e, nil
+}
+
+type resolveUndoDecoder struct {
+	r io.Reader
+}
+
+func (d *resolveUndoDecoder) Decode(ru *ResolveUndo) error {
+	for {
+		e, err := d.readEntry()
+		if err != nil {
+			if err == io.EOF {
+				return nil
+			}
+
+			return err
+		}
+
+		ru.Entries = append(ru.Entries, *e)
+	}
+}
+
+func (d *resolveUndoDecoder) readEntry() (*ResolveUndoEntry, error) {
+	e := &ResolveUndoEntry{
+		Stages: make(map[Stage]plumbing.Hash),
+	}
+
+	path, err := binary.ReadUntil(d.r, '\x00')
+	if err != nil {
+		return nil, err
+	}
+
+	e.Path = string(path)
+
+	for i := 0; i < 3; i++ {
+		if err := d.readStage(e, Stage(i+1)); err != nil {
+			return nil, err
+		}
+	}
+
+	for s := range e.Stages {
+		var hash plumbing.Hash
+		if err := binary.Read(d.r, hash[:]); err != nil {
+			return nil, err
+		}
+
+		e.Stages[s] = hash
+	}
+
+	return e, nil
+}
+
+func (d *resolveUndoDecoder) readStage(e *ResolveUndoEntry, s Stage) error {
+	ascii, err := binary.ReadUntil(d.r, '\x00')
+	if err != nil {
+		return err
+	}
+
+	stage, err := strconv.ParseInt(string(ascii), 8, 64)
+	if err != nil {
+		return err
+	}
+
+	if stage != 0 {
+		e.Stages[s] = plumbing.ZeroHash
+	}
+
+	return nil
+}
+
+type endOfIndexEntryDecoder struct {
+	r io.Reader
+}
+
+func (d *endOfIndexEntryDecoder) Decode(e *EndOfIndexEntry) error {
+	var err error
+	e.Offset, err = binary.ReadUint32(d.r)
+	if err != nil {
+		return err
+	}
+
+	return binary.Read(d.r, &e.Hash)
+}

vendor/gopkg.in/src-d/go-git.v4/plumbing/format/index/doc.go

@@ -0,0 +1,360 @@
+// Package index implements encoding and decoding of index format files.
+//
+//    Git index format
+//    ================
+//
+//    == The Git index file has the following format
+//
+//      All binary numbers are in network byte order. Version 2 is described
+//      here unless stated otherwise.
+//
+//      - A 12-byte header consisting of
+//
+//        4-byte signature:
+//          The signature is { 'D', 'I', 'R', 'C' } (stands for "dircache")
+//
+//        4-byte version number:
+//          The current supported versions are 2, 3 and 4.
+//
+//        32-bit number of index entries.
+//
+//      - A number of sorted index entries (see below).
+//
+//      - Extensions
+//
+//        Extensions are identified by signature. Optional extensions can
+//        be ignored if Git does not understand them.
+//
+//        Git currently supports cached tree and resolve undo extensions.
+//
+//        4-byte extension signature. If the first byte is 'A'..'Z' the
+//        extension is optional and can be ignored.
+//
+//        32-bit size of the extension
+//
+//        Extension data
+//
+//      - 160-bit SHA-1 over the content of the index file before this
+//        checksum.
+//
+//    == Index entry
+//
+//      Index entries are sorted in ascending order on the name field,
+//      interpreted as a string of unsigned bytes (i.e. memcmp() order, no
+//      localization, no special casing of directory separator '/'). Entries
+//      with the same name are sorted by their stage field.
+//
+//      32-bit ctime seconds, the last time a file's metadata changed
+//        this is stat(2) data
+//
+//      32-bit ctime nanosecond fractions
+//        this is stat(2) data
+//
+//      32-bit mtime seconds, the last time a file's data changed
+//        this is stat(2) data
+//
+//      32-bit mtime nanosecond fractions
+//        this is stat(2) data
+//
+//      32-bit dev
+//        this is stat(2) data
+//
+//      32-bit ino
+//        this is stat(2) data
+//
+//      32-bit mode, split into (high to low bits)
+//
+//        4-bit object type
+//          valid values in binary are 1000 (regular file), 1010 (symbolic link)
+//          and 1110 (gitlink)
+//
+//        3-bit unused
+//
+//        9-bit unix permission. Only 0755 and 0644 are valid for regular files.
+//        Symbolic links and gitlinks have value 0 in this field.
+//
+//      32-bit uid
+//        this is stat(2) data
+//
+//      32-bit gid
+//        this is stat(2) data
+//
+//      32-bit file size
+//        This is the on-disk size from stat(2), truncated to 32-bit.
+//
+//      160-bit SHA-1 for the represented object
+//
+//      A 16-bit 'flags' field split into (high to low bits)
+//
+//        1-bit assume-valid flag
+//
+//        1-bit extended flag (must be zero in version 2)
+//
+//        2-bit stage (during merge)
+//
+//        12-bit name length if the length is less than 0xFFF; otherwise 0xFFF
+//        is stored in this field.
+//
+//      (Version 3 or later) A 16-bit field, only applicable if the
+//      "extended flag" above is 1, split into (high to low bits).
+//
+//        1-bit reserved for future
+//
+//        1-bit skip-worktree flag (used by sparse checkout)
+//
+//        1-bit intent-to-add flag (used by "git add -N")
+//
+//        13-bit unused, must be zero
+//
+//      Entry path name (variable length) relative to top level directory
+//        (without leading slash). '/' is used as path separator. The special
+//        path components ".", ".." and ".git" (without quotes) are disallowed.
+//        Trailing slash is also disallowed.
+//
+//        The exact encoding is undefined, but the '.' and '/' characters
+//        are encoded in 7-bit ASCII and the encoding cannot contain a NUL
+//        byte (iow, this is a UNIX pathname).
+//
+//      (Version 4) In version 4, the entry path name is prefix-compressed
+//        relative to the path name for the previous entry (the very first
+//        entry is encoded as if the path name for the previous entry is an
+//        empty string).  At the beginning of an entry, an integer N in the
+//        variable width encoding (the same encoding as the offset is encoded
+//        for OFS_DELTA pack entries; see pack-format.txt) is stored, followed
+//        by a NUL-terminated string S.  Removing N bytes from the end of the
+//        path name for the previous entry, and replacing it with the string S
+//        yields the path name for this entry.
+//
+//      1-8 nul bytes as necessary to pad the entry to a multiple of eight bytes
+//      while keeping the name NUL-terminated.
+//
+//      (Version 4) In version 4, the padding after the pathname does not
+//      exist.
+//
+//      Interpretation of index entries in split index mode is completely
+//      different. See below for details.
+//
+//    == Extensions
+//
+//    === Cached tree
+//
+//      Cached tree extension contains pre-computed hashes for trees that can
+//      be derived from the index. It helps speed up tree object generation
+//      from index for a new commit.
+//
+//      When a path is updated in index, the path must be invalidated and
+//      removed from tree cache.
+//
+//      The signature for this extension is { 'T', 'R', 'E', 'E' }.
+//
+//      A series of entries fill the entire extension; each of which
+//      consists of:
+//
+//      - NUL-terminated path component (relative to its parent directory);
+//
+//      - ASCII decimal number of entries in the index that is covered by the
+//        tree this entry represents (entry_count);
+//
+//      - A space (ASCII 32);
+//
+//      - ASCII decimal number that represents the number of subtrees this
+//        tree has;
+//
+//      - A newline (ASCII 10); and
+//
+//      - 160-bit object name for the object that would result from writing
+//        this span of index as a tree.
+//
+//      An entry can be in an invalidated state and is represented by having
+//      a negative number in the entry_count field. In this case, there is no
+//      object name and the next entry starts immediately after the newline.
+//      When writing an invalid entry, -1 should always be used as entry_count.
+//
+//      The entries are written out in the top-down, depth-first order.  The
+//      first entry represents the root level of the repository, followed by the
+//      first subtree--let's call this A--of the root level (with its name
+//      relative to the root level), followed by the first subtree of A (with
+//      its name relative to A), ...
+//
+//    === Resolve undo
+//
+//      A conflict is represented in the index as a set of higher stage entries.
+//      When a conflict is resolved (e.g. with "git add path"), these higher
+//      stage entries will be removed and a stage-0 entry with proper resolution
+//      is added.
+//
+//      When these higher stage entries are removed, they are saved in the
+//      resolve undo extension, so that conflicts can be recreated (e.g. with
+//      "git checkout -m"), in case users want to redo a conflict resolution
+//      from scratch.
+//
+//      The signature for this extension is { 'R', 'E', 'U', 'C' }.
+//
+//      A series of entries fill the entire extension; each of which
+//      consists of:
+//
+//      - NUL-terminated pathname the entry describes (relative to the root of
+//        the repository, i.e. full pathname);
+//
+//      - Three NUL-terminated ASCII octal numbers, entry mode of entries in
+//        stage 1 to 3 (a missing stage is represented by "0" in this field);
+//        and
+//
+//      - At most three 160-bit object names of the entry in stages from 1 to 3
+//        (nothing is written for a missing stage).
+//
+//    === Split index
+//
+//      In split index mode, the majority of index entries could be stored
+//      in a separate file. This extension records the changes to be made on
+//      top of that to produce the final index.
+//
+//      The signature for this extension is { 'l', 'i', 'n', 'k' }.
+//
+//      The extension consists of:
+//
+//      - 160-bit SHA-1 of the shared index file. The shared index file path
+//        is $GIT_DIR/sharedindex.<SHA-1>. If all 160 bits are zero, the
+//        index does not require a shared index file.
+//
+//      - An ewah-encoded delete bitmap, each bit represents an entry in the
+//        shared index. If a bit is set, its corresponding entry in the
+//        shared index will be removed from the final index.  Note, because
+//        a delete operation changes index entry positions, but we do need
+//        original positions in replace phase, it's best to just mark
+//        entries for removal, then do a mass deletion after replacement.
+//
+//      - An ewah-encoded replace bitmap, each bit represents an entry in
+//        the shared index. If a bit is set, its corresponding entry in the
+//        shared index will be replaced with an entry in this index
+//        file. All replaced entries are stored in sorted order in this
+//        index. The first "1" bit in the replace bitmap corresponds to the
+//        first index entry, the second "1" bit to the second entry and so
+//        on. Replaced entries may have empty path names to save space.
+//
+//      The remaining index entries after replaced ones will be added to the
+//      final index. These added entries are also sorted by entry name then
+//      stage.
+//
+//    == Untracked cache
+//
+//      Untracked cache saves the untracked file list and necessary data to
+//      verify the cache. The signature for this extension is { 'U', 'N',
+//      'T', 'R' }.
+//
+//      The extension starts with
+//
+//      - A sequence of NUL-terminated strings, preceded by the size of the
+//        sequence in variable width encoding. Each string describes the
+//        environment where the cache can be used.
+//
+//      - Stat data of $GIT_DIR/info/exclude. See "Index entry" section from
+//        ctime field until "file size".
+//
+//      - Stat data of plumbing.excludesfile
+//
+//      - 32-bit dir_flags (see struct dir_struct)
+//
+//      - 160-bit SHA-1 of $GIT_DIR/info/exclude. Null SHA-1 means the file
+//        does not exist.
+//
+//      - 160-bit SHA-1 of plumbing.excludesfile. Null SHA-1 means the file does
+//        not exist.
+//
+//      - NUL-terminated string of per-dir exclude file name. This usually
+//        is ".gitignore".
+//
+//      - The number of following directory blocks, variable width
+//        encoding. If this number is zero, the extension ends here with a
+//        following NUL.
+//
+//      - A number of directory blocks in depth-first-search order, each
+//        consists of
+//
+//        - The number of untracked entries, variable width encoding.
+//
+//        - The number of sub-directory blocks, variable width encoding.
+//
+//        - The directory name terminated by NUL.
+//
+//        - A number of untracked file/dir names terminated by NUL.
+//
+//    The remaining data of each directory block is grouped by type:
+//
+//      - An ewah bitmap, the n-th bit marks whether the n-th directory has
+//        valid untracked cache entries.
+//
+//      - An ewah bitmap, the n-th bit records "check-only" bit of
+//        read_directory_recursive() for the n-th directory.
+//
+//      - An ewah bitmap, the n-th bit indicates whether SHA-1 and stat data
+//        is valid for the n-th directory and exists in the next data.
+//
+//      - An array of stat data. The n-th data corresponds with the n-th
+//        "one" bit in the previous ewah bitmap.
+//
+//      - An array of SHA-1. The n-th SHA-1 corresponds with the n-th "one" bit
+//        in the previous ewah bitmap.
+//
+//      - One NUL.
+//
+//   == File System Monitor cache
+//
+//     The file system monitor cache tracks files for which the core.fsmonitor
+//     hook has told us about changes.  The signature for this extension is
+//     { 'F', 'S', 'M', 'N' }.
+//
+//     The extension starts with
+//
+//     - 32-bit version number: the current supported version is 1.
+//
+//     - 64-bit time: the extension data reflects all changes through the given
+//       time which is stored as the nanoseconds elapsed since midnight,
+//       January 1, 1970.
+//
+//    - 32-bit bitmap size: the size of the CE_FSMONITOR_VALID bitmap.
+//
+//    - An ewah bitmap, the n-th bit indicates whether the n-th index entry
+//      is not CE_FSMONITOR_VALID.
+//
+//  == End of Index Entry
+//
+//    The End of Index Entry (EOIE) is used to locate the end of the variable
+//    length index entries and the begining of the extensions. Code can take
+//    advantage of this to quickly locate the index extensions without having
+//    to parse through all of the index entries.
+//
+//    Because it must be able to be loaded before the variable length cache
+//    entries and other index extensions, this extension must be written last.
+//    The signature for this extension is { 'E', 'O', 'I', 'E' }.
+//
+//    The extension consists of:
+//
+//    - 32-bit offset to the end of the index entries
+//
+//    - 160-bit SHA-1 over the extension types and their sizes (but not
+//      their contents).  E.g. if we have "TREE" extension that is N-bytes
+//      long, "REUC" extension that is M-bytes long, followed by "EOIE",
+//      then the hash would be:
+//
+//      SHA-1("TREE" + <binary representation of N> +
+//        "REUC" + <binary representation of M>)
+//
+//  == Index Entry Offset Table
+//
+//    The Index Entry Offset Table (IEOT) is used to help address the CPU
+//    cost of loading the index by enabling multi-threading the process of
+//    converting cache entries from the on-disk format to the in-memory format.
+//    The signature for this extension is { 'I', 'E', 'O', 'T' }.
+//
+//    The extension consists of:
+//
+//    - 32-bit version (currently 1)
+//
+//    - A number of index offset entries each consisting of:
+//
+//    - 32-bit offset from the begining of the file to the first cache entry
+//      in this block of entries.
+//
+//    - 32-bit count of cache entries in this blockpackage index
+package index

vendor/gopkg.in/src-d/go-git.v4/plumbing/format/index/encoder.go

@@ -0,0 +1,150 @@
+package index
+
+import (
+	"bytes"
+	"crypto/sha1"
+	"errors"
+	"hash"
+	"io"
+	"sort"
+	"time"
+
+	"gopkg.in/src-d/go-git.v4/utils/binary"
+)
+
+var (
+	// EncodeVersionSupported is the range of supported index versions
+	EncodeVersionSupported uint32 = 2
+
+	// ErrInvalidTimestamp is returned by Encode if a Index with a Entry with
+	// negative timestamp values
+	ErrInvalidTimestamp = errors.New("negative timestamps are not allowed")
+)
+
+// An Encoder writes an Index to an output stream.
+type Encoder struct {
+	w    io.Writer
+	hash hash.Hash
+}
+
+// NewEncoder returns a new encoder that writes to w.
+func NewEncoder(w io.Writer) *Encoder {
+	h := sha1.New()
+	mw := io.MultiWriter(w, h)
+	return &Encoder{mw, h}
+}
+
+// Encode writes the Index to the stream of the encoder.
+func (e *Encoder) Encode(idx *Index) error {
+	// TODO: support versions v3 and v4
+	// TODO: support extensions
+	if idx.Version != EncodeVersionSupported {
+		return ErrUnsupportedVersion
+	}
+
+	if err := e.encodeHeader(idx); err != nil {
+		return err
+	}
+
+	if err := e.encodeEntries(idx); err != nil {
+		return err
+	}
+
+	return e.encodeFooter()
+}
+
+func (e *Encoder) encodeHeader(idx *Index) error {
+	return binary.Write(e.w,
+		indexSignature,
+		idx.Version,
+		uint32(len(idx.Entries)),
+	)
+}
+
+func (e *Encoder) encodeEntries(idx *Index) error {
+	sort.Sort(byName(idx.Entries))
+
+	for _, entry := range idx.Entries {
+		if err := e.encodeEntry(entry); err != nil {
+			return err
+		}
+
+		wrote := entryHeaderLength + len(entry.Name)
+		if err := e.padEntry(wrote); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func (e *Encoder) encodeEntry(entry *Entry) error {
+	if entry.IntentToAdd || entry.SkipWorktree {
+		return ErrUnsupportedVersion
+	}
+
+	sec, nsec, err := e.timeToUint32(&entry.CreatedAt)
+	if err != nil {
+		return err
+	}
+
+	msec, mnsec, err := e.timeToUint32(&entry.ModifiedAt)
+	if err != nil {
+		return err
+	}
+
+	flags := uint16(entry.Stage&0x3) << 12
+	if l := len(entry.Name); l < nameMask {
+		flags |= uint16(l)
+	} else {
+		flags |= nameMask
+	}
+
+	flow := []interface{}{
+		sec, nsec,
+		msec, mnsec,
+		entry.Dev,
+		entry.Inode,
+		entry.Mode,
+		entry.UID,
+		entry.GID,
+		entry.Size,
+		entry.Hash[:],
+		flags,
+	}
+
+	if err := binary.Write(e.w, flow...); err != nil {
+		return err
+	}
+
+	return binary.Write(e.w, []byte(entry.Name))
+}
+
+func (e *Encoder) timeToUint32(t *time.Time) (uint32, uint32, error) {
+	if t.IsZero() {
+		return 0, 0, nil
+	}
+
+	if t.Unix() < 0 || t.UnixNano() < 0 {
+		return 0, 0, ErrInvalidTimestamp
+	}
+
+	return uint32(t.Unix()), uint32(t.Nanosecond()), nil
+}
+
+func (e *Encoder) padEntry(wrote int) error {
+	padLen := 8 - wrote%8
+
+	_, err := e.w.Write(bytes.Repeat([]byte{'\x00'}, padLen))
+	return err
+}
+
+func (e *Encoder) encodeFooter() error {
+	return binary.Write(e.w, e.hash.Sum(nil))
+}
+
+type byName []*Entry
+
+func (l byName) Len() int           { return len(l) }
+func (l byName) Swap(i, j int)      { l[i], l[j] = l[j], l[i] }
+func (l byName) Less(i, j int) bool { return l[i].Name < l[j].Name }

vendor/gopkg.in/src-d/go-git.v4/plumbing/format/index/index.go

@@ -0,0 +1,213 @@
+package index
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"path/filepath"
+	"time"
+
+	"gopkg.in/src-d/go-git.v4/plumbing"
+	"gopkg.in/src-d/go-git.v4/plumbing/filemode"
+)
+
+var (
+	// ErrUnsupportedVersion is returned by Decode when the index file version
+	// is not supported.
+	ErrUnsupportedVersion = errors.New("unsupported version")
+	// ErrEntryNotFound is returned by Index.Entry, if an entry is not found.
+	ErrEntryNotFound = errors.New("entry not found")
+
+	indexSignature              = []byte{'D', 'I', 'R', 'C'}
+	treeExtSignature            = []byte{'T', 'R', 'E', 'E'}
+	resolveUndoExtSignature     = []byte{'R', 'E', 'U', 'C'}
+	endOfIndexEntryExtSignature = []byte{'E', 'O', 'I', 'E'}
+)
+
+// Stage during merge
+type Stage int
+
+const (
+	// Merged is the default stage, fully merged
+	Merged Stage = 1
+	// AncestorMode is the base revision
+	AncestorMode Stage = 1
+	// OurMode is the first tree revision, ours
+	OurMode Stage = 2
+	// TheirMode is the second tree revision, theirs
+	TheirMode Stage = 3
+)
+
+// Index contains the information about which objects are currently checked out
+// in the worktree, having information about the working files. Changes in
+// worktree are detected using this Index. The Index is also used during merges
+type Index struct {
+	// Version is index version
+	Version uint32
+	// Entries collection of entries represented by this Index. The order of
+	// this collection is not guaranteed
+	Entries []*Entry
+	// Cache represents the 'Cached tree' extension
+	Cache *Tree
+	// ResolveUndo represents the 'Resolve undo' extension
+	ResolveUndo *ResolveUndo
+	// EndOfIndexEntry represents the 'End of Index Entry' extension
+	EndOfIndexEntry *EndOfIndexEntry
+}
+
+// Add creates a new Entry and returns it. The caller should first check that
+// another entry with the same path does not exist.
+func (i *Index) Add(path string) *Entry {
+	e := &Entry{
+		Name: filepath.ToSlash(path),
+	}
+
+	i.Entries = append(i.Entries, e)
+	return e
+}
+
+// Entry returns the entry that match the given path, if any.
+func (i *Index) Entry(path string) (*Entry, error) {
+	path = filepath.ToSlash(path)
+	for _, e := range i.Entries {
+		if e.Name == path {
+			return e, nil
+		}
+	}
+
+	return nil, ErrEntryNotFound
+}
+
+// Remove remove the entry that match the give path and returns deleted entry.
+func (i *Index) Remove(path string) (*Entry, error) {
+	path = filepath.ToSlash(path)
+	for index, e := range i.Entries {
+		if e.Name == path {
+			i.Entries = append(i.Entries[:index], i.Entries[index+1:]...)
+			return e, nil
+		}
+	}
+
+	return nil, ErrEntryNotFound
+}
+
+// Glob returns the all entries matching pattern or nil if there is no matching
+// entry. The syntax of patterns is the same as in filepath.Glob.
+func (i *Index) Glob(pattern string) (matches []*Entry, err error) {
+	pattern = filepath.ToSlash(pattern)
+	for _, e := range i.Entries {
+		m, err := match(pattern, e.Name)
+		if err != nil {
+			return nil, err
+		}
+
+		if m {
+			matches = append(matches, e)
+		}
+	}
+
+	return
+}
+
+// String is equivalent to `git ls-files --stage --debug`
+func (i *Index) String() string {
+	buf := bytes.NewBuffer(nil)
+	for _, e := range i.Entries {
+		buf.WriteString(e.String())
+	}
+
+	return buf.String()
+}
+
+// Entry represents a single file (or stage of a file) in the cache. An entry
+// represents exactly one stage of a file. If a file path is unmerged then
+// multiple Entry instances may appear for the same path name.
+type Entry struct {
+	// Hash is the SHA1 of the represented file
+	Hash plumbing.Hash
+	// Name is the  Entry path name relative to top level directory
+	Name string
+	// CreatedAt time when the tracked path was created
+	CreatedAt time.Time
+	// ModifiedAt time when the tracked path was changed
+	ModifiedAt time.Time
+	// Dev and Inode of the tracked path
+	Dev, Inode uint32
+	// Mode of the path
+	Mode filemode.FileMode
+	// UID and GID, userid and group id of the owner
+	UID, GID uint32
+	// Size is the length in bytes for regular files
+	Size uint32
+	// Stage on a merge is defines what stage is representing this entry
+	// https://git-scm.com/book/en/v2/Git-Tools-Advanced-Merging
+	Stage Stage
+	// SkipWorktree used in sparse checkouts
+	// https://git-scm.com/docs/git-read-tree#_sparse_checkout
+	SkipWorktree bool
+	// IntentToAdd record only the fact that the path will be added later
+	// https://git-scm.com/docs/git-add ("git add -N")
+	IntentToAdd bool
+}
+
+func (e Entry) String() string {
+	buf := bytes.NewBuffer(nil)
+
+	fmt.Fprintf(buf, "%06o %s %d\t%s\n", e.Mode, e.Hash, e.Stage, e.Name)
+	fmt.Fprintf(buf, "  ctime: %d:%d\n", e.CreatedAt.Unix(), e.CreatedAt.Nanosecond())
+	fmt.Fprintf(buf, "  mtime: %d:%d\n", e.ModifiedAt.Unix(), e.ModifiedAt.Nanosecond())
+	fmt.Fprintf(buf, "  dev: %d\tino: %d\n", e.Dev, e.Inode)
+	fmt.Fprintf(buf, "  uid: %d\tgid: %d\n", e.UID, e.GID)
+	fmt.Fprintf(buf, "  size: %d\tflags: %x\n", e.Size, 0)
+
+	return buf.String()
+}
+
+// Tree contains pre-computed hashes for trees that can be derived from the
+// index. It helps speed up tree object generation from index for a new commit.
+type Tree struct {
+	Entries []TreeEntry
+}
+
+// TreeEntry entry of a cached Tree
+type TreeEntry struct {
+	// Path component (relative to its parent directory)
+	Path string
+	// Entries is the number of entries in the index that is covered by the tree
+	// this entry represents.
+	Entries int
+	// Trees is the number that represents the number of subtrees this tree has
+	Trees int
+	// Hash object name for the object that would result from writing this span
+	// of index as a tree.
+	Hash plumbing.Hash
+}
+
+// ResolveUndo is used when a conflict is resolved (e.g. with "git add path"),
+// these higher stage entries are removed and a stage-0 entry with proper
+// resolution is added. When these higher stage entries are removed, they are
+// saved in the resolve undo extension.
+type ResolveUndo struct {
+	Entries []ResolveUndoEntry
+}
+
+// ResolveUndoEntry contains the information about a conflict when is resolved
+type ResolveUndoEntry struct {
+	Path   string
+	Stages map[Stage]plumbing.Hash
+}
+
+// EndOfIndexEntry is the End of Index Entry (EOIE) is used to locate the end of
+// the variable length index entries and the begining of the extensions. Code
+// can take advantage of this to quickly locate the index extensions without
+// having to parse through all of the index entries.
+//
+//  Because it must be able to be loaded before the variable length cache
+//  entries and other index extensions, this extension must be written last.
+type EndOfIndexEntry struct {
+	// Offset to the end of the index entries
+	Offset uint32
+	// Hash is a SHA-1 over the extension types and their sizes (but not
+	//	their contents).
+	Hash plumbing.Hash
+}

vendor/gopkg.in/src-d/go-git.v4/plumbing/format/index/match.go

@@ -0,0 +1,186 @@
+package index
+
+import (
+	"path/filepath"
+	"runtime"
+	"unicode/utf8"
+)
+
+// match is filepath.Match with support to match fullpath and not only filenames
+// code from:
+// https://github.com/golang/go/blob/39852bf4cce6927e01d0136c7843f65a801738cb/src/path/filepath/match.go#L44-L224
+func match(pattern, name string) (matched bool, err error) {
+Pattern:
+	for len(pattern) > 0 {
+		var star bool
+		var chunk string
+		star, chunk, pattern = scanChunk(pattern)
+
+		// Look for match at current position.
+		t, ok, err := matchChunk(chunk, name)
+		// if we're the last chunk, make sure we've exhausted the name
+		// otherwise we'll give a false result even if we could still match
+		// using the star
+		if ok && (len(t) == 0 || len(pattern) > 0) {
+			name = t
+			continue
+		}
+		if err != nil {
+			return false, err
+		}
+		if star {
+			// Look for match skipping i+1 bytes.
+			// Cannot skip /.
+			for i := 0; i < len(name); i++ {
+				t, ok, err := matchChunk(chunk, name[i+1:])
+				if ok {
+					// if we're the last chunk, make sure we exhausted the name
+					if len(pattern) == 0 && len(t) > 0 {
+						continue
+					}
+					name = t
+					continue Pattern
+				}
+				if err != nil {
+					return false, err
+				}
+			}
+		}
+		return false, nil
+	}
+	return len(name) == 0, nil
+}
+
+// scanChunk gets the next segment of pattern, which is a non-star string
+// possibly preceded by a star.
+func scanChunk(pattern string) (star bool, chunk, rest string) {
+	for len(pattern) > 0 && pattern[0] == '*' {
+		pattern = pattern[1:]
+		star = true
+	}
+	inrange := false
+	var i int
+Scan:
+	for i = 0; i < len(pattern); i++ {
+		switch pattern[i] {
+		case '\\':
+			if runtime.GOOS != "windows" {
+				// error check handled in matchChunk: bad pattern.
+				if i+1 < len(pattern) {
+					i++
+				}
+			}
+		case '[':
+			inrange = true
+		case ']':
+			inrange = false
+		case '*':
+			if !inrange {
+				break Scan
+			}
+		}
+	}
+	return star, pattern[0:i], pattern[i:]
+}
+
+// matchChunk checks whether chunk matches the beginning of s.
+// If so, it returns the remainder of s (after the match).
+// Chunk is all single-character operators: literals, char classes, and ?.
+func matchChunk(chunk, s string) (rest string, ok bool, err error) {
+	for len(chunk) > 0 {
+		if len(s) == 0 {
+			return
+		}
+		switch chunk[0] {
+		case '[':
+			// character class
+			r, n := utf8.DecodeRuneInString(s)
+			s = s[n:]
+			chunk = chunk[1:]
+			// We can't end right after '[', we're expecting at least
+			// a closing bracket and possibly a caret.
+			if len(chunk) == 0 {
+				err = filepath.ErrBadPattern
+				return
+			}
+			// possibly negated
+			negated := chunk[0] == '^'
+			if negated {
+				chunk = chunk[1:]
+			}
+			// parse all ranges
+			match := false
+			nrange := 0
+			for {
+				if len(chunk) > 0 && chunk[0] == ']' && nrange > 0 {
+					chunk = chunk[1:]
+					break
+				}
+				var lo, hi rune
+				if lo, chunk, err = getEsc(chunk); err != nil {
+					return
+				}
+				hi = lo
+				if chunk[0] == '-' {
+					if hi, chunk, err = getEsc(chunk[1:]); err != nil {
+						return
+					}
+				}
+				if lo <= r && r <= hi {
+					match = true
+				}
+				nrange++
+			}
+			if match == negated {
+				return
+			}
+
+		case '?':
+			_, n := utf8.DecodeRuneInString(s)
+			s = s[n:]
+			chunk = chunk[1:]
+
+		case '\\':
+			if runtime.GOOS != "windows" {
+				chunk = chunk[1:]
+				if len(chunk) == 0 {
+					err = filepath.ErrBadPattern
+					return
+				}
+			}
+			fallthrough
+
+		default:
+			if chunk[0] != s[0] {
+				return
+			}
+			s = s[1:]
+			chunk = chunk[1:]
+		}
+	}
+	return s, true, nil
+}
+
+// getEsc gets a possibly-escaped character from chunk, for a character class.
+func getEsc(chunk string) (r rune, nchunk string, err error) {
+	if len(chunk) == 0 || chunk[0] == '-' || chunk[0] == ']' {
+		err = filepath.ErrBadPattern
+		return
+	}
+	if chunk[0] == '\\' && runtime.GOOS != "windows" {
+		chunk = chunk[1:]
+		if len(chunk) == 0 {
+			err = filepath.ErrBadPattern
+			return
+		}
+	}
+	r, n := utf8.DecodeRuneInString(chunk)
+	if r == utf8.RuneError && n == 1 {
+		err = filepath.ErrBadPattern
+	}
+	nchunk = chunk[n:]
+	if len(nchunk) == 0 {
+		err = filepath.ErrBadPattern
+	}
+	return
+}

vendor/gopkg.in/src-d/go-git.v4/plumbing/format/objfile/doc.go

@@ -0,0 +1,2 @@
+// Package objfile implements encoding and decoding of object files.
+package objfile

vendor/gopkg.in/src-d/go-git.v4/plumbing/format/objfile/reader.go

@@ -0,0 +1,114 @@
+package objfile
+
+import (
+	"compress/zlib"
+	"errors"
+	"io"
+	"strconv"
+
+	"gopkg.in/src-d/go-git.v4/plumbing"
+	"gopkg.in/src-d/go-git.v4/plumbing/format/packfile"
+)
+
+var (
+	ErrClosed       = errors.New("objfile: already closed")
+	ErrHeader       = errors.New("objfile: invalid header")
+	ErrNegativeSize = errors.New("objfile: negative object size")
+)
+
+// Reader reads and decodes compressed objfile data from a provided io.Reader.
+// Reader implements io.ReadCloser. Close should be called when finished with
+// the Reader. Close will not close the underlying io.Reader.
+type Reader struct {
+	multi  io.Reader
+	zlib   io.ReadCloser
+	hasher plumbing.Hasher
+}
+
+// NewReader returns a new Reader reading from r.
+func NewReader(r io.Reader) (*Reader, error) {
+	zlib, err := zlib.NewReader(r)
+	if err != nil {
+		return nil, packfile.ErrZLib.AddDetails(err.Error())
+	}
+
+	return &Reader{
+		zlib: zlib,
+	}, nil
+}
+
+// Header reads the type and the size of object, and prepares the reader for read
+func (r *Reader) Header() (t plumbing.ObjectType, size int64, err error) {
+	var raw []byte
+	raw, err = r.readUntil(' ')
+	if err != nil {
+		return
+	}
+
+	t, err = plumbing.ParseObjectType(string(raw))
+	if err != nil {
+		return
+	}
+
+	raw, err = r.readUntil(0)
+	if err != nil {
+		return
+	}
+
+	size, err = strconv.ParseInt(string(raw), 10, 64)
+	if err != nil {
+		err = ErrHeader
+		return
+	}
+
+	defer r.prepareForRead(t, size)
+	return
+}
+
+// readSlice reads one byte at a time from r until it encounters delim or an
+// error.
+func (r *Reader) readUntil(delim byte) ([]byte, error) {
+	var buf [1]byte
+	value := make([]byte, 0, 16)
+	for {
+		if n, err := r.zlib.Read(buf[:]); err != nil && (err != io.EOF || n == 0) {
+			if err == io.EOF {
+				return nil, ErrHeader
+			}
+			return nil, err
+		}
+
+		if buf[0] == delim {
+			return value, nil
+		}
+
+		value = append(value, buf[0])
+	}
+}
+
+func (r *Reader) prepareForRead(t plumbing.ObjectType, size int64) {
+	r.hasher = plumbing.NewHasher(t, size)
+	r.multi = io.TeeReader(r.zlib, r.hasher)
+}
+
+// Read reads len(p) bytes into p from the object data stream. It returns
+// the number of bytes read (0 <= n <= len(p)) and any error encountered. Even
+// if Read returns n < len(p), it may use all of p as scratch space during the
+// call.
+//
+// If Read encounters the end of the data stream it will return err == io.EOF,
+// either in the current call if n > 0 or in a subsequent call.
+func (r *Reader) Read(p []byte) (n int, err error) {
+	return r.multi.Read(p)
+}
+
+// Hash returns the hash of the object data stream that has been read so far.
+func (r *Reader) Hash() plumbing.Hash {
+	return r.hasher.Sum()
+}
+
+// Close releases any resources consumed by the Reader. Calling Close does not
+// close the wrapped io.Reader originally passed to NewReader.
+func (r *Reader) Close() error {
+	return r.zlib.Close()
+}

vendor/gopkg.in/src-d/go-git.v4/plumbing/format/objfile/writer.go

@@ -0,0 +1,109 @@
+package objfile
+
+import (
+	"compress/zlib"
+	"errors"
+	"io"
+	"strconv"
+
+	"gopkg.in/src-d/go-git.v4/plumbing"
+)
+
+var (
+	ErrOverflow = errors.New("objfile: declared data length exceeded (overflow)")
+)
+
+// Writer writes and encodes data in compressed objfile format to a provided
+// io.Writer. Close should be called when finished with the Writer. Close will
+// not close the underlying io.Writer.
+type Writer struct {
+	raw    io.Writer
+	zlib   io.WriteCloser
+	hasher plumbing.Hasher
+	multi  io.Writer
+
+	closed  bool
+	pending int64 // number of unwritten bytes
+}
+
+// NewWriter returns a new Writer writing to w.
+//
+// The returned Writer implements io.WriteCloser. Close should be called when
+// finished with the Writer. Close will not close the underlying io.Writer.
+func NewWriter(w io.Writer) *Writer {
+	return &Writer{
+		raw:  w,
+		zlib: zlib.NewWriter(w),
+	}
+}
+
+// WriteHeader writes the type and the size and prepares to accept the object's
+// contents. If an invalid t is provided, plumbing.ErrInvalidType is returned. If a
+// negative size is provided, ErrNegativeSize is returned.
+func (w *Writer) WriteHeader(t plumbing.ObjectType, size int64) error {
+	if !t.Valid() {
+		return plumbing.ErrInvalidType
+	}
+	if size < 0 {
+		return ErrNegativeSize
+	}
+
+	b := t.Bytes()
+	b = append(b, ' ')
+	b = append(b, []byte(strconv.FormatInt(size, 10))...)
+	b = append(b, 0)
+
+	defer w.prepareForWrite(t, size)
+	_, err := w.zlib.Write(b)
+
+	return err
+}
+
+func (w *Writer) prepareForWrite(t plumbing.ObjectType, size int64) {
+	w.pending = size
+
+	w.hasher = plumbing.NewHasher(t, size)
+	w.multi = io.MultiWriter(w.zlib, w.hasher)
+}
+
+// Write writes the object's contents. Write returns the error ErrOverflow if
+// more than size bytes are written after WriteHeader.
+func (w *Writer) Write(p []byte) (n int, err error) {
+	if w.closed {
+		return 0, ErrClosed
+	}
+
+	overwrite := false
+	if int64(len(p)) > w.pending {
+		p = p[0:w.pending]
+		overwrite = true
+	}
+
+	n, err = w.multi.Write(p)
+	w.pending -= int64(n)
+	if err == nil && overwrite {
+		err = ErrOverflow
+		return
+	}
+
+	return
+}
+
+// Hash returns the hash of the object data stream that has been written so far.
+// It can be called before or after Close.
+func (w *Writer) Hash() plumbing.Hash {
+	return w.hasher.Sum() // Not yet closed, return hash of data written so far
+}
+
+// Close releases any resources consumed by the Writer.
+//
+// Calling Close does not close the wrapped io.Writer originally passed to
+// NewWriter.
+func (w *Writer) Close() error {
+	if err := w.zlib.Close(); err != nil {
+		return err
+	}
+
+	w.closed = true
+	return nil
+}

vendor/gopkg.in/src-d/go-git.v4/plumbing/format/packfile/common.go

@@ -0,0 +1,68 @@
+package packfile
+
+import (
+	"bytes"
+	"io"
+	"sync"
+
+	"gopkg.in/src-d/go-git.v4/plumbing/storer"
+	"gopkg.in/src-d/go-git.v4/utils/ioutil"
+)
+
+var signature = []byte{'P', 'A', 'C', 'K'}
+
+const (
+	// VersionSupported is the packfile version supported by this package
+	VersionSupported uint32 = 2
+
+	firstLengthBits = uint8(4)   // the first byte into object header has 4 bits to store the length
+	lengthBits      = uint8(7)   // subsequent bytes has 7 bits to store the length
+	maskFirstLength = 15         // 0000 1111
+	maskContinue    = 0x80       // 1000 0000
+	maskLength      = uint8(127) // 0111 1111
+	maskType        = uint8(112) // 0111 0000
+)
+
+// UpdateObjectStorage updates the storer with the objects in the given
+// packfile.
+func UpdateObjectStorage(s storer.Storer, packfile io.Reader) error {
+	if pw, ok := s.(storer.PackfileWriter); ok {
+		return WritePackfileToObjectStorage(pw, packfile)
+	}
+
+	p, err := NewParserWithStorage(NewScanner(packfile), s)
+	if err != nil {
+		return err
+	}
+
+	_, err = p.Parse()
+	return err
+}
+
+// WritePackfileToObjectStorage writes all the packfile objects into the given
+// object storage.
+func WritePackfileToObjectStorage(
+	sw storer.PackfileWriter,
+	packfile io.Reader,
+) (err error) {
+	w, err := sw.PackfileWriter()
+	if err != nil {
+		return err
+	}
+
+	defer ioutil.CheckClose(w, &err)
+
+	var n int64
+	n, err = io.Copy(w, packfile)
+	if err == nil && n == 0 {
+		return ErrEmptyPackfile
+	}
+
+	return err
+}
+
+var bufPool = sync.Pool{
+	New: func() interface{} {
+		return bytes.NewBuffer(nil)
+	},
+}

vendor/gopkg.in/src-d/go-git.v4/plumbing/format/packfile/delta_index.go

@@ -0,0 +1,297 @@
+package packfile
+
+const blksz = 16
+const maxChainLength = 64
+
+// deltaIndex is a modified version of JGit's DeltaIndex adapted to our current
+// design.
+type deltaIndex struct {
+	table   []int
+	entries []int
+	mask    int
+}
+
+func (idx *deltaIndex) init(buf []byte) {
+	scanner := newDeltaIndexScanner(buf, len(buf))
+	idx.mask = scanner.mask
+	idx.table = scanner.table
+	idx.entries = make([]int, countEntries(scanner)+1)
+	idx.copyEntries(scanner)
+}
+
+// findMatch returns the offset of src where the block starting at tgtOffset
+// is and the length of the match. A length of 0 means there was no match. A
+// length of -1 means the src length is lower than the blksz and whatever
+// other positive length is the length of the match in bytes.
+func (idx *deltaIndex) findMatch(src, tgt []byte, tgtOffset int) (srcOffset, l int) {
+	if len(tgt) < tgtOffset+s {
+		return 0, len(tgt) - tgtOffset
+	}
+
+	if len(src) < blksz {
+		return 0, -1
+	}
+
+	if len(tgt) >= tgtOffset+s && len(src) >= blksz {
+		h := hashBlock(tgt, tgtOffset)
+		tIdx := h & idx.mask
+		eIdx := idx.table[tIdx]
+		if eIdx != 0 {
+			srcOffset = idx.entries[eIdx]
+		} else {
+			return
+		}
+
+		l = matchLength(src, tgt, tgtOffset, srcOffset)
+	}
+
+	return
+}
+
+func matchLength(src, tgt []byte, otgt, osrc int) (l int) {
+	lensrc := len(src)
+	lentgt := len(tgt)
+	for (osrc < lensrc && otgt < lentgt) && src[osrc] == tgt[otgt] {
+		l++
+		osrc++
+		otgt++
+	}
+	return
+}
+
+func countEntries(scan *deltaIndexScanner) (cnt int) {
+	// Figure out exactly how many entries we need. As we do the
+	// enumeration truncate any delta chains longer than what we
+	// are willing to scan during encode. This keeps the encode
+	// logic linear in the size of the input rather than quadratic.
+	for i := 0; i < len(scan.table); i++ {
+		h := scan.table[i]
+		if h == 0 {
+			continue
+		}
+
+		size := 0
+		for {
+			size++
+			if size == maxChainLength {
+				scan.next[h] = 0
+				break
+			}
+			h = scan.next[h]
+
+			if h == 0 {
+				break
+			}
+		}
+		cnt += size
+	}
+
+	return
+}
+
+func (idx *deltaIndex) copyEntries(scanner *deltaIndexScanner) {
+	// Rebuild the entries list from the scanner, positioning all
+	// blocks in the same hash chain next to each other. We can
+	// then later discard the next list, along with the scanner.
+	//
+	next := 1
+	for i := 0; i < len(idx.table); i++ {
+		h := idx.table[i]
+		if h == 0 {
+			continue
+		}
+
+		idx.table[i] = next
+		for {
+			idx.entries[next] = scanner.entries[h]
+			next++
+			h = scanner.next[h]
+
+			if h == 0 {
+				break
+			}
+		}
+	}
+}
+
+type deltaIndexScanner struct {
+	table   []int
+	entries []int
+	next    []int
+	mask    int
+	count   int
+}
+
+func newDeltaIndexScanner(buf []byte, size int) *deltaIndexScanner {
+	size -= size % blksz
+	worstCaseBlockCnt := size / blksz
+	if worstCaseBlockCnt < 1 {
+		return new(deltaIndexScanner)
+	}
+
+	tableSize := tableSize(worstCaseBlockCnt)
+	scanner := &deltaIndexScanner{
+		table:   make([]int, tableSize),
+		mask:    tableSize - 1,
+		entries: make([]int, worstCaseBlockCnt+1),
+		next:    make([]int, worstCaseBlockCnt+1),
+	}
+
+	scanner.scan(buf, size)
+	return scanner
+}
+
+// slightly modified version of JGit's DeltaIndexScanner. We store the offset on the entries
+// instead of the entries and the key, so we avoid operations to retrieve the offset later, as
+// we don't use the key.
+// See: https://github.com/eclipse/jgit/blob/005e5feb4ecd08c4e4d141a38b9e7942accb3212/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/pack/DeltaIndexScanner.java
+func (s *deltaIndexScanner) scan(buf []byte, end int) {
+	lastHash := 0
+	ptr := end - blksz
+
+	for {
+		key := hashBlock(buf, ptr)
+		tIdx := key & s.mask
+		head := s.table[tIdx]
+		if head != 0 && lastHash == key {
+			s.entries[head] = ptr
+		} else {
+			s.count++
+			eIdx := s.count
+			s.entries[eIdx] = ptr
+			s.next[eIdx] = head
+			s.table[tIdx] = eIdx
+		}
+
+		lastHash = key
+		ptr -= blksz
+
+		if 0 > ptr {
+			break
+		}
+	}
+}
+
+func tableSize(worstCaseBlockCnt int) int {
+	shift := 32 - leadingZeros(uint32(worstCaseBlockCnt))
+	sz := 1 << uint(shift-1)
+	if sz < worstCaseBlockCnt {
+		sz <<= 1
+	}
+	return sz
+}
+
+// use https://golang.org/pkg/math/bits/#LeadingZeros32 in the future
+func leadingZeros(x uint32) (n int) {
+	if x >= 1<<16 {
+		x >>= 16
+		n = 16
+	}
+	if x >= 1<<8 {
+		x >>= 8
+		n += 8
+	}
+	n += int(len8tab[x])
+	return 32 - n
+}
+
+var len8tab = [256]uint8{
+	0x00, 0x01, 0x02, 0x02, 0x03, 0x03, 0x03, 0x03, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04,
+	0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05,
+	0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06,
+	0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06,
+	0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07,
+	0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07,
+	0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07,
+	0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07,
+	0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08,
+	0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08,
+	0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08,
+	0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08,
+	0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08,
+	0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08,
+	0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08,
+	0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08,
+}
+
+func hashBlock(raw []byte, ptr int) int {
+	// The first 4 steps collapse out into a 4 byte big-endian decode,
+	// with a larger right shift as we combined shift lefts together.
+	//
+	hash := ((uint32(raw[ptr]) & 0xff) << 24) |
+		((uint32(raw[ptr+1]) & 0xff) << 16) |
+		((uint32(raw[ptr+2]) & 0xff) << 8) |
+		(uint32(raw[ptr+3]) & 0xff)
+	hash ^= T[hash>>31]
+
+	hash = ((hash << 8) | (uint32(raw[ptr+4]) & 0xff)) ^ T[hash>>23]
+	hash = ((hash << 8) | (uint32(raw[ptr+5]) & 0xff)) ^ T[hash>>23]
+	hash = ((hash << 8) | (uint32(raw[ptr+6]) & 0xff)) ^ T[hash>>23]
+	hash = ((hash << 8) | (uint32(raw[ptr+7]) & 0xff)) ^ T[hash>>23]
+
+	hash = ((hash << 8) | (uint32(raw[ptr+8]) & 0xff)) ^ T[hash>>23]
+	hash = ((hash << 8) | (uint32(raw[ptr+9]) & 0xff)) ^ T[hash>>23]
+	hash = ((hash << 8) | (uint32(raw[ptr+10]) & 0xff)) ^ T[hash>>23]
+	hash = ((hash << 8) | (uint32(raw[ptr+11]) & 0xff)) ^ T[hash>>23]
+
+	hash = ((hash << 8) | (uint32(raw[ptr+12]) & 0xff)) ^ T[hash>>23]
+	hash = ((hash << 8) | (uint32(raw[ptr+13]) & 0xff)) ^ T[hash>>23]
+	hash = ((hash << 8) | (uint32(raw[ptr+14]) & 0xff)) ^ T[hash>>23]
+	hash = ((hash << 8) | (uint32(raw[ptr+15]) & 0xff)) ^ T[hash>>23]
+
+	return int(hash)
+}
+
+var T = []uint32{0x00000000, 0xd4c6b32d, 0x7d4bd577,
+	0xa98d665a, 0x2e5119c3, 0xfa97aaee, 0x531accb4, 0x87dc7f99,
+	0x5ca23386, 0x886480ab, 0x21e9e6f1, 0xf52f55dc, 0x72f32a45,
+	0xa6359968, 0x0fb8ff32, 0xdb7e4c1f, 0x6d82d421, 0xb944670c,
+	0x10c90156, 0xc40fb27b, 0x43d3cde2, 0x97157ecf, 0x3e981895,
+	0xea5eabb8, 0x3120e7a7, 0xe5e6548a, 0x4c6b32d0, 0x98ad81fd,
+	0x1f71fe64, 0xcbb74d49, 0x623a2b13, 0xb6fc983e, 0x0fc31b6f,
+	0xdb05a842, 0x7288ce18, 0xa64e7d35, 0x219202ac, 0xf554b181,
+	0x5cd9d7db, 0x881f64f6, 0x536128e9, 0x87a79bc4, 0x2e2afd9e,
+	0xfaec4eb3, 0x7d30312a, 0xa9f68207, 0x007be45d, 0xd4bd5770,
+	0x6241cf4e, 0xb6877c63, 0x1f0a1a39, 0xcbcca914, 0x4c10d68d,
+	0x98d665a0, 0x315b03fa, 0xe59db0d7, 0x3ee3fcc8, 0xea254fe5,
+	0x43a829bf, 0x976e9a92, 0x10b2e50b, 0xc4745626, 0x6df9307c,
+	0xb93f8351, 0x1f8636de, 0xcb4085f3, 0x62cde3a9, 0xb60b5084,
+	0x31d72f1d, 0xe5119c30, 0x4c9cfa6a, 0x985a4947, 0x43240558,
+	0x97e2b675, 0x3e6fd02f, 0xeaa96302, 0x6d751c9b, 0xb9b3afb6,
+	0x103ec9ec, 0xc4f87ac1, 0x7204e2ff, 0xa6c251d2, 0x0f4f3788,
+	0xdb8984a5, 0x5c55fb3c, 0x88934811, 0x211e2e4b, 0xf5d89d66,
+	0x2ea6d179, 0xfa606254, 0x53ed040e, 0x872bb723, 0x00f7c8ba,
+	0xd4317b97, 0x7dbc1dcd, 0xa97aaee0, 0x10452db1, 0xc4839e9c,
+	0x6d0ef8c6, 0xb9c84beb, 0x3e143472, 0xead2875f, 0x435fe105,
+	0x97995228, 0x4ce71e37, 0x9821ad1a, 0x31accb40, 0xe56a786d,
+	0x62b607f4, 0xb670b4d9, 0x1ffdd283, 0xcb3b61ae, 0x7dc7f990,
+	0xa9014abd, 0x008c2ce7, 0xd44a9fca, 0x5396e053, 0x8750537e,
+	0x2edd3524, 0xfa1b8609, 0x2165ca16, 0xf5a3793b, 0x5c2e1f61,
+	0x88e8ac4c, 0x0f34d3d5, 0xdbf260f8, 0x727f06a2, 0xa6b9b58f,
+	0x3f0c6dbc, 0xebcade91, 0x4247b8cb, 0x96810be6, 0x115d747f,
+	0xc59bc752, 0x6c16a108, 0xb8d01225, 0x63ae5e3a, 0xb768ed17,
+	0x1ee58b4d, 0xca233860, 0x4dff47f9, 0x9939f4d4, 0x30b4928e,
+	0xe47221a3, 0x528eb99d, 0x86480ab0, 0x2fc56cea, 0xfb03dfc7,
+	0x7cdfa05e, 0xa8191373, 0x01947529, 0xd552c604, 0x0e2c8a1b,
+	0xdaea3936, 0x73675f6c, 0xa7a1ec41, 0x207d93d8, 0xf4bb20f5,
+	0x5d3646af, 0x89f0f582, 0x30cf76d3, 0xe409c5fe, 0x4d84a3a4,
+	0x99421089, 0x1e9e6f10, 0xca58dc3d, 0x63d5ba67, 0xb713094a,
+	0x6c6d4555, 0xb8abf678, 0x11269022, 0xc5e0230f, 0x423c5c96,
+	0x96faefbb, 0x3f7789e1, 0xebb13acc, 0x5d4da2f2, 0x898b11df,
+	0x20067785, 0xf4c0c4a8, 0x731cbb31, 0xa7da081c, 0x0e576e46,
+	0xda91dd6b, 0x01ef9174, 0xd5292259, 0x7ca44403, 0xa862f72e,
+	0x2fbe88b7, 0xfb783b9a, 0x52f55dc0, 0x8633eeed, 0x208a5b62,
+	0xf44ce84f, 0x5dc18e15, 0x89073d38, 0x0edb42a1, 0xda1df18c,
+	0x739097d6, 0xa75624fb, 0x7c2868e4, 0xa8eedbc9, 0x0163bd93,
+	0xd5a50ebe, 0x52797127, 0x86bfc20a, 0x2f32a450, 0xfbf4177d,
+	0x4d088f43, 0x99ce3c6e, 0x30435a34, 0xe485e919, 0x63599680,
+	0xb79f25ad, 0x1e1243f7, 0xcad4f0da, 0x11aabcc5, 0xc56c0fe8,
+	0x6ce169b2, 0xb827da9f, 0x3ffba506, 0xeb3d162b, 0x42b07071,
+	0x9676c35c, 0x2f49400d, 0xfb8ff320, 0x5202957a, 0x86c42657,
+	0x011859ce, 0xd5deeae3, 0x7c538cb9, 0xa8953f94, 0x73eb738b,
+	0xa72dc0a6, 0x0ea0a6fc, 0xda6615d1, 0x5dba6a48, 0x897cd965,
+	0x20f1bf3f, 0xf4370c12, 0x42cb942c, 0x960d2701, 0x3f80415b,
+	0xeb46f276, 0x6c9a8def, 0xb85c3ec2, 0x11d15898, 0xc517ebb5,
+	0x1e69a7aa, 0xcaaf1487, 0x632272dd, 0xb7e4c1f0, 0x3038be69,
+	0xe4fe0d44, 0x4d736b1e, 0x99b5d833,
+}

vendor/gopkg.in/src-d/go-git.v4/plumbing/format/packfile/delta_selector.go

@@ -0,0 +1,369 @@
+package packfile
+
+import (
+	"sort"
+	"sync"
+
+	"gopkg.in/src-d/go-git.v4/plumbing"
+	"gopkg.in/src-d/go-git.v4/plumbing/storer"
+)
+
+const (
+	// deltas based on deltas, how many steps we can do.
+	// 50 is the default value used in JGit
+	maxDepth = int64(50)
+)
+
+// applyDelta is the set of object types that we should apply deltas
+var applyDelta = map[plumbing.ObjectType]bool{
+	plumbing.BlobObject: true,
+	plumbing.TreeObject: true,
+}
+
+type deltaSelector struct {
+	storer storer.EncodedObjectStorer
+}
+
+func newDeltaSelector(s storer.EncodedObjectStorer) *deltaSelector {
+	return &deltaSelector{s}
+}
+
+// ObjectsToPack creates a list of ObjectToPack from the hashes
+// provided, creating deltas if it's suitable, using an specific
+// internal logic.  `packWindow` specifies the size of the sliding
+// window used to compare objects for delta compression; 0 turns off
+// delta compression entirely.
+func (dw *deltaSelector) ObjectsToPack(
+	hashes []plumbing.Hash,
+	packWindow uint,
+) ([]*ObjectToPack, error) {
+	otp, err := dw.objectsToPack(hashes, packWindow)
+	if err != nil {
+		return nil, err
+	}
+
+	if packWindow == 0 {
+		return otp, nil
+	}
+
+	dw.sort(otp)
+
+	var objectGroups [][]*ObjectToPack
+	var prev *ObjectToPack
+	i := -1
+	for _, obj := range otp {
+		if prev == nil || prev.Type() != obj.Type() {
+			objectGroups = append(objectGroups, []*ObjectToPack{obj})
+			i++
+			prev = obj
+		} else {
+			objectGroups[i] = append(objectGroups[i], obj)
+		}
+	}
+
+	var wg sync.WaitGroup
+	var once sync.Once
+	for _, objs := range objectGroups {
+		objs := objs
+		wg.Add(1)
+		go func() {
+			if walkErr := dw.walk(objs, packWindow); walkErr != nil {
+				once.Do(func() {
+					err = walkErr
+				})
+			}
+			wg.Done()
+		}()
+	}
+	wg.Wait()
+
+	if err != nil {
+		return nil, err
+	}
+
+	return otp, nil
+}
+
+func (dw *deltaSelector) objectsToPack(
+	hashes []plumbing.Hash,
+	packWindow uint,
+) ([]*ObjectToPack, error) {
+	var objectsToPack []*ObjectToPack
+	for _, h := range hashes {
+		var o plumbing.EncodedObject
+		var err error
+		if packWindow == 0 {
+			o, err = dw.encodedObject(h)
+		} else {
+			o, err = dw.encodedDeltaObject(h)
+		}
+		if err != nil {
+			return nil, err
+		}
+
+		otp := newObjectToPack(o)
+		if _, ok := o.(plumbing.DeltaObject); ok {
+			otp.CleanOriginal()
+		}
+
+		objectsToPack = append(objectsToPack, otp)
+	}
+
+	if packWindow == 0 {
+		return objectsToPack, nil
+	}
+
+	if err := dw.fixAndBreakChains(objectsToPack); err != nil {
+		return nil, err
+	}
+
+	return objectsToPack, nil
+}
+
+func (dw *deltaSelector) encodedDeltaObject(h plumbing.Hash) (plumbing.EncodedObject, error) {
+	edos, ok := dw.storer.(storer.DeltaObjectStorer)
+	if !ok {
+		return dw.encodedObject(h)
+	}
+
+	return edos.DeltaObject(plumbing.AnyObject, h)
+}
+
+func (dw *deltaSelector) encodedObject(h plumbing.Hash) (plumbing.EncodedObject, error) {
+	return dw.storer.EncodedObject(plumbing.AnyObject, h)
+}
+
+func (dw *deltaSelector) fixAndBreakChains(objectsToPack []*ObjectToPack) error {
+	m := make(map[plumbing.Hash]*ObjectToPack, len(objectsToPack))
+	for _, otp := range objectsToPack {
+		m[otp.Hash()] = otp
+	}
+
+	for _, otp := range objectsToPack {
+		if err := dw.fixAndBreakChainsOne(m, otp); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func (dw *deltaSelector) fixAndBreakChainsOne(objectsToPack map[plumbing.Hash]*ObjectToPack, otp *ObjectToPack) error {
+	if !otp.Object.Type().IsDelta() {
+		return nil
+	}
+
+	// Initial ObjectToPack instances might have a delta assigned to Object
+	// but no actual base initially. Once Base is assigned to a delta, it means
+	// we already fixed it.
+	if otp.Base != nil {
+		return nil
+	}
+
+	do, ok := otp.Object.(plumbing.DeltaObject)
+	if !ok {
+		// if this is not a DeltaObject, then we cannot retrieve its base,
+		// so we have to break the delta chain here.
+		return dw.undeltify(otp)
+	}
+
+	base, ok := objectsToPack[do.BaseHash()]
+	if !ok {
+		// The base of the delta is not in our list of objects to pack, so
+		// we break the chain.
+		return dw.undeltify(otp)
+	}
+
+	if err := dw.fixAndBreakChainsOne(objectsToPack, base); err != nil {
+		return err
+	}
+
+	otp.SetDelta(base, otp.Object)
+	return nil
+}
+
+func (dw *deltaSelector) restoreOriginal(otp *ObjectToPack) error {
+	if otp.Original != nil {
+		return nil
+	}
+
+	if !otp.Object.Type().IsDelta() {
+		return nil
+	}
+
+	obj, err := dw.encodedObject(otp.Hash())
+	if err != nil {
+		return err
+	}
+
+	otp.SetOriginal(obj)
+
+	return nil
+}
+
+// undeltify undeltifies an *ObjectToPack by retrieving the original object from
+// the storer and resetting it.
+func (dw *deltaSelector) undeltify(otp *ObjectToPack) error {
+	if err := dw.restoreOriginal(otp); err != nil {
+		return err
+	}
+
+	otp.Object = otp.Original
+	otp.Depth = 0
+	return nil
+}
+
+func (dw *deltaSelector) sort(objectsToPack []*ObjectToPack) {
+	sort.Sort(byTypeAndSize(objectsToPack))
+}
+
+func (dw *deltaSelector) walk(
+	objectsToPack []*ObjectToPack,
+	packWindow uint,
+) error {
+	indexMap := make(map[plumbing.Hash]*deltaIndex)
+	for i := 0; i < len(objectsToPack); i++ {
+		// Clean up the index map and reconstructed delta objects for anything
+		// outside our pack window, to save memory.
+		if i > int(packWindow) {
+			obj := objectsToPack[i-int(packWindow)]
+
+			delete(indexMap, obj.Hash())
+
+			if obj.IsDelta() {
+				obj.SaveOriginalMetadata()
+				obj.CleanOriginal()
+			}
+		}
+
+		target := objectsToPack[i]
+
+		// If we already have a delta, we don't try to find a new one for this
+		// object. This happens when a delta is set to be reused from an existing
+		// packfile.
+		if target.IsDelta() {
+			continue
+		}
+
+		// We only want to create deltas from specific types.
+		if !applyDelta[target.Type()] {
+			continue
+		}
+
+		for j := i - 1; j >= 0 && i-j < int(packWindow); j-- {
+			base := objectsToPack[j]
+			// Objects must use only the same type as their delta base.
+			// Since objectsToPack is sorted by type and size, once we find
+			// a different type, we know we won't find more of them.
+			if base.Type() != target.Type() {
+				break
+			}
+
+			if err := dw.tryToDeltify(indexMap, base, target); err != nil {
+				return err
+			}
+		}
+	}
+
+	return nil
+}
+
+func (dw *deltaSelector) tryToDeltify(indexMap map[plumbing.Hash]*deltaIndex, base, target *ObjectToPack) error {
+	// Original object might not be present if we're reusing a delta, so we
+	// ensure it is restored.
+	if err := dw.restoreOriginal(target); err != nil {
+		return err
+	}
+
+	if err := dw.restoreOriginal(base); err != nil {
+		return err
+	}
+
+	// If the sizes are radically different, this is a bad pairing.
+	if target.Size() < base.Size()>>4 {
+		return nil
+	}
+
+	msz := dw.deltaSizeLimit(
+		target.Object.Size(),
+		base.Depth,
+		target.Depth,
+		target.IsDelta(),
+	)
+
+	// Nearly impossible to fit useful delta.
+	if msz <= 8 {
+		return nil
+	}
+
+	// If we have to insert a lot to make this work, find another.
+	if base.Size()-target.Size() > msz {
+		return nil
+	}
+
+	if _, ok := indexMap[base.Hash()]; !ok {
+		indexMap[base.Hash()] = new(deltaIndex)
+	}
+
+	// Now we can generate the delta using originals
+	delta, err := getDelta(indexMap[base.Hash()], base.Original, target.Original)
+	if err != nil {
+		return err
+	}
+
+	// if delta better than target
+	if delta.Size() < msz {
+		target.SetDelta(base, delta)
+	}
+
+	return nil
+}
+
+func (dw *deltaSelector) deltaSizeLimit(targetSize int64, baseDepth int,
+	targetDepth int, targetDelta bool) int64 {
+	if !targetDelta {
+		// Any delta should be no more than 50% of the original size
+		// (for text files deflate of whole form should shrink 50%).
+		n := targetSize >> 1
+
+		// Evenly distribute delta size limits over allowed depth.
+		// If src is non-delta (depth = 0), delta <= 50% of original.
+		// If src is almost at limit (9/10), delta <= 10% of original.
+		return n * (maxDepth - int64(baseDepth)) / maxDepth
+	}
+
+	// With a delta base chosen any new delta must be "better".
+	// Retain the distribution described above.
+	d := int64(targetDepth)
+	n := targetSize
+
+	// If target depth is bigger than maxDepth, this delta is not suitable to be used.
+	if d >= maxDepth {
+		return 0
+	}
+
+	// If src is whole (depth=0) and base is near limit (depth=9/10)
+	// any delta using src can be 10x larger and still be better.
+	//
+	// If src is near limit (depth=9/10) and base is whole (depth=0)
+	// a new delta dependent on src must be 1/10th the size.
+	return n * (maxDepth - int64(baseDepth)) / (maxDepth - d)
+}
+
+type byTypeAndSize []*ObjectToPack
+
+func (a byTypeAndSize) Len() int { return len(a) }
+
+func (a byTypeAndSize) Swap(i, j int) { a[i], a[j] = a[j], a[i] }
+
+func (a byTypeAndSize) Less(i, j int) bool {
+	if a[i].Type() < a[j].Type() {
+		return false
+	}
+
+	if a[i].Type() > a[j].Type() {
+		return true
+	}
+
+	return a[i].Size() > a[j].Size()
+}

vendor/gopkg.in/src-d/go-git.v4/plumbing/format/packfile/diff_delta.go

@@ -0,0 +1,201 @@
+package packfile
+
+import (
+	"bytes"
+
+	"gopkg.in/src-d/go-git.v4/plumbing"
+)
+
+// See https://github.com/jelmer/dulwich/blob/master/dulwich/pack.py and
+// https://github.com/tarruda/node-git-core/blob/master/src/js/delta.js
+// for more info
+
+const (
+	// Standard chunk size used to generate fingerprints
+	s = 16
+
+	// https://github.com/git/git/blob/f7466e94375b3be27f229c78873f0acf8301c0a5/diff-delta.c#L428
+	// Max size of a copy operation (64KB)
+	maxCopySize = 64 * 1024
+)
+
+// GetDelta returns an EncodedObject of type OFSDeltaObject. Base and Target object,
+// will be loaded into memory to be able to create the delta object.
+// To generate target again, you will need the obtained object and "base" one.
+// Error will be returned if base or target object cannot be read.
+func GetDelta(base, target plumbing.EncodedObject) (plumbing.EncodedObject, error) {
+	return getDelta(new(deltaIndex), base, target)
+}
+
+func getDelta(index *deltaIndex, base, target plumbing.EncodedObject) (plumbing.EncodedObject, error) {
+	br, err := base.Reader()
+	if err != nil {
+		return nil, err
+	}
+	defer br.Close()
+	tr, err := target.Reader()
+	if err != nil {
+		return nil, err
+	}
+	defer tr.Close()
+
+	bb := bufPool.Get().(*bytes.Buffer)
+	bb.Reset()
+	defer bufPool.Put(bb)
+
+	_, err = bb.ReadFrom(br)
+	if err != nil {
+		return nil, err
+	}
+
+	tb := bufPool.Get().(*bytes.Buffer)
+	tb.Reset()
+	defer bufPool.Put(tb)
+
+	_, err = tb.ReadFrom(tr)
+	if err != nil {
+		return nil, err
+	}
+
+	db := diffDelta(index, bb.Bytes(), tb.Bytes())
+	delta := &plumbing.MemoryObject{}
+	_, err = delta.Write(db)
+	if err != nil {
+		return nil, err
+	}
+
+	delta.SetSize(int64(len(db)))
+	delta.SetType(plumbing.OFSDeltaObject)
+
+	return delta, nil
+}
+
+// DiffDelta returns the delta that transforms src into tgt.
+func DiffDelta(src, tgt []byte) []byte {
+	return diffDelta(new(deltaIndex), src, tgt)
+}
+
+func diffDelta(index *deltaIndex, src []byte, tgt []byte) []byte {
+	buf := bufPool.Get().(*bytes.Buffer)
+	buf.Reset()
+	buf.Write(deltaEncodeSize(len(src)))
+	buf.Write(deltaEncodeSize(len(tgt)))
+
+	if len(index.entries) == 0 {
+		index.init(src)
+	}
+
+	ibuf := bufPool.Get().(*bytes.Buffer)
+	ibuf.Reset()
+	for i := 0; i < len(tgt); i++ {
+		offset, l := index.findMatch(src, tgt, i)
+
+		if l == 0 {
+			// couldn't find a match, just write the current byte and continue
+			ibuf.WriteByte(tgt[i])
+		} else if l < 0 {
+			// src is less than blksz, copy the rest of the target to avoid
+			// calls to findMatch
+			for ; i < len(tgt); i++ {
+				ibuf.WriteByte(tgt[i])
+			}
+		} else if l < s {
+			// remaining target is less than blksz, copy what's left of it
+			// and avoid calls to findMatch
+			for j := i; j < i+l; j++ {
+				ibuf.WriteByte(tgt[j])
+			}
+			i += l - 1
+		} else {
+			encodeInsertOperation(ibuf, buf)
+
+			rl := l
+			aOffset := offset
+			for rl > 0 {
+				if rl < maxCopySize {
+					buf.Write(encodeCopyOperation(aOffset, rl))
+					break
+				}
+
+				buf.Write(encodeCopyOperation(aOffset, maxCopySize))
+				rl -= maxCopySize
+				aOffset += maxCopySize
+			}
+
+			i += l - 1
+		}
+	}
+
+	encodeInsertOperation(ibuf, buf)
+	bytes := buf.Bytes()
+
+	bufPool.Put(buf)
+	bufPool.Put(ibuf)
+
+	return bytes
+}
+
+func encodeInsertOperation(ibuf, buf *bytes.Buffer) {
+	if ibuf.Len() == 0 {
+		return
+	}
+
+	b := ibuf.Bytes()
+	s := ibuf.Len()
+	o := 0
+	for {
+		if s <= 127 {
+			break
+		}
+		buf.WriteByte(byte(127))
+		buf.Write(b[o : o+127])
+		s -= 127
+		o += 127
+	}
+	buf.WriteByte(byte(s))
+	buf.Write(b[o : o+s])
+
+	ibuf.Reset()
+}
+
+func deltaEncodeSize(size int) []byte {
+	var ret []byte
+	c := size & 0x7f
+	size >>= 7
+	for {
+		if size == 0 {
+			break
+		}
+
+		ret = append(ret, byte(c|0x80))
+		c = size & 0x7f
+		size >>= 7
+	}
+	ret = append(ret, byte(c))
+
+	return ret
+}
+
+func encodeCopyOperation(offset, length int) []byte {
+	code := 0x80
+	var opcodes []byte
+
+	var i uint
+	for i = 0; i < 4; i++ {
+		f := 0xff << (i * 8)
+		if offset&f != 0 {
+			opcodes = append(opcodes, byte(offset&f>>(i*8)))
+			code |= 0x01 << i
+		}
+	}
+
+	for i = 0; i < 3; i++ {
+		f := 0xff << (i * 8)
+		if length&f != 0 {
+			opcodes = append(opcodes, byte(length&f>>(i*8)))
+			code |= 0x10 << i
+		}
+	}
+
+	return append([]byte{byte(code)}, opcodes...)
+}

vendor/gopkg.in/src-d/go-git.v4/plumbing/format/packfile/doc.go

@@ -0,0 +1,39 @@
+// Package packfile implements encoding and decoding of packfile format.
+//
+//  == pack-*.pack files have the following format:
+//
+//    - A header appears at the beginning and consists of the following:
+//
+//      4-byte signature:
+//          The signature is: {'P', 'A', 'C', 'K'}
+//
+//      4-byte version number (network byte order):
+//          GIT currently accepts version number 2 or 3 but
+//          generates version 2 only.
+//
+//      4-byte number of objects contained in the pack (network byte order)
+//
+//      Observation: we cannot have more than 4G versions ;-) and
+//      more than 4G objects in a pack.
+//
+//    - The header is followed by number of object entries, each of
+//      which looks like this:
+//
+//      (undeltified representation)
+//      n-byte type and length (3-bit type, (n-1)*7+4-bit length)
+//      compressed data
+//
+//      (deltified representation)
+//      n-byte type and length (3-bit type, (n-1)*7+4-bit length)
+//      20-byte base object name
+//      compressed delta data
+//
+//      Observation: length of each object is encoded in a variable
+//      length format and is not constrained to 32-bit or anything.
+//
+//   - The trailer records 20-byte SHA1 checksum of all of the above.
+//
+//
+// Source:
+// https://www.kernel.org/pub/software/scm/git/docs/v1.7.5/technical/pack-protocol.txt
+package packfile

vendor/gopkg.in/src-d/go-git.v4/plumbing/format/packfile/encoder.go

@@ -0,0 +1,219 @@
+package packfile
+
+import (
+	"compress/zlib"
+	"crypto/sha1"
+	"fmt"
+	"io"
+
+	"gopkg.in/src-d/go-git.v4/plumbing"
+	"gopkg.in/src-d/go-git.v4/plumbing/storer"
+	"gopkg.in/src-d/go-git.v4/utils/binary"
+)
+
+// Encoder gets the data from the storage and write it into the writer in PACK
+// format
+type Encoder struct {
+	selector *deltaSelector
+	w        *offsetWriter
+	zw       *zlib.Writer
+	hasher   plumbing.Hasher
+
+	useRefDeltas bool
+}
+
+// NewEncoder creates a new packfile encoder using a specific Writer and
+// EncodedObjectStorer. By default deltas used to generate the packfile will be
+// OFSDeltaObject. To use Reference deltas, set useRefDeltas to true.
+func NewEncoder(w io.Writer, s storer.EncodedObjectStorer, useRefDeltas bool) *Encoder {
+	h := plumbing.Hasher{
+		Hash: sha1.New(),
+	}
+	mw := io.MultiWriter(w, h)
+	ow := newOffsetWriter(mw)
+	zw := zlib.NewWriter(mw)
+	return &Encoder{
+		selector:     newDeltaSelector(s),
+		w:            ow,
+		zw:           zw,
+		hasher:       h,
+		useRefDeltas: useRefDeltas,
+	}
+}
+
+// Encode creates a packfile containing all the objects referenced in
+// hashes and writes it to the writer in the Encoder.  `packWindow`
+// specifies the size of the sliding window used to compare objects
+// for delta compression; 0 turns off delta compression entirely.
+func (e *Encoder) Encode(
+	hashes []plumbing.Hash,
+	packWindow uint,
+) (plumbing.Hash, error) {
+	objects, err := e.selector.ObjectsToPack(hashes, packWindow)
+	if err != nil {
+		return plumbing.ZeroHash, err
+	}
+
+	return e.encode(objects)
+}
+
+func (e *Encoder) encode(objects []*ObjectToPack) (plumbing.Hash, error) {
+	if err := e.head(len(objects)); err != nil {
+		return plumbing.ZeroHash, err
+	}
+
+	for _, o := range objects {
+		if err := e.entry(o); err != nil {
+			return plumbing.ZeroHash, err
+		}
+	}
+
+	return e.footer()
+}
+
+func (e *Encoder) head(numEntries int) error {
+	return binary.Write(
+		e.w,
+		signature,
+		int32(VersionSupported),
+		int32(numEntries),
+	)
+}
+
+func (e *Encoder) entry(o *ObjectToPack) error {
+	if o.WantWrite() {
+		// A cycle exists in this delta chain. This should only occur if a
+		// selected object representation disappeared during writing
+		// (for example due to a concurrent repack) and a different base
+		// was chosen, forcing a cycle. Select something other than a
+		// delta, and write this object.
+		e.selector.restoreOriginal(o)
+		o.BackToOriginal()
+	}
+
+	if o.IsWritten() {
+		return nil
+	}
+
+	o.MarkWantWrite()
+
+	if err := e.writeBaseIfDelta(o); err != nil {
+		return err
+	}
+
+	// We need to check if we already write that object due a cyclic delta chain
+	if o.IsWritten() {
+		return nil
+	}
+
+	o.Offset = e.w.Offset()
+
+	if o.IsDelta() {
+		if err := e.writeDeltaHeader(o); err != nil {
+			return err
+		}
+	} else {
+		if err := e.entryHead(o.Type(), o.Size()); err != nil {
+			return err
+		}
+	}
+
+	e.zw.Reset(e.w)
+	or, err := o.Object.Reader()
+	if err != nil {
+		return err
+	}
+
+	_, err = io.Copy(e.zw, or)
+	if err != nil {
+		return err
+	}
+
+	return e.zw.Close()
+}
+
+func (e *Encoder) writeBaseIfDelta(o *ObjectToPack) error {
+	if o.IsDelta() && !o.Base.IsWritten() {
+		// We must write base first
+		return e.entry(o.Base)
+	}
+
+	return nil
+}
+
+func (e *Encoder) writeDeltaHeader(o *ObjectToPack) error {
+	// Write offset deltas by default
+	t := plumbing.OFSDeltaObject
+	if e.useRefDeltas {
+		t = plumbing.REFDeltaObject
+	}
+
+	if err := e.entryHead(t, o.Object.Size()); err != nil {
+		return err
+	}
+
+	if e.useRefDeltas {
+		return e.writeRefDeltaHeader(o.Base.Hash())
+	} else {
+		return e.writeOfsDeltaHeader(o)
+	}
+}
+
+func (e *Encoder) writeRefDeltaHeader(base plumbing.Hash) error {
+	return binary.Write(e.w, base)
+}
+
+func (e *Encoder) writeOfsDeltaHeader(o *ObjectToPack) error {
+	// for OFS_DELTA, offset of the base is interpreted as negative offset
+	// relative to the type-byte of the header of the ofs-delta entry.
+	relativeOffset := o.Offset - o.Base.Offset
+	if relativeOffset <= 0 {
+		return fmt.Errorf("bad offset for OFS_DELTA entry: %d", relativeOffset)
+	}
+
+	return binary.WriteVariableWidthInt(e.w, relativeOffset)
+}
+
+func (e *Encoder) entryHead(typeNum plumbing.ObjectType, size int64) error {
+	t := int64(typeNum)
+	header := []byte{}
+	c := (t << firstLengthBits) | (size & maskFirstLength)
+	size >>= firstLengthBits
+	for {
+		if size == 0 {
+			break
+		}
+		header = append(header, byte(c|maskContinue))
+		c = size & int64(maskLength)
+		size >>= lengthBits
+	}
+
+	header = append(header, byte(c))
+	_, err := e.w.Write(header)
+
+	return err
+}
+
+func (e *Encoder) footer() (plumbing.Hash, error) {
+	h := e.hasher.Sum()
+	return h, binary.Write(e.w, h)
+}
+
+type offsetWriter struct {
+	w      io.Writer
+	offset int64
+}
+
+func newOffsetWriter(w io.Writer) *offsetWriter {
+	return &offsetWriter{w: w}
+}
+
+func (ow *offsetWriter) Write(p []byte) (n int, err error) {
+	n, err = ow.w.Write(p)
+	ow.offset += int64(n)
+	return n, err
+}
+
+func (ow *offsetWriter) Offset() int64 {
+	return ow.offset
+}

vendor/gopkg.in/src-d/go-git.v4/plumbing/format/packfile/error.go

@@ -0,0 +1,30 @@
+package packfile
+
+import "fmt"
+
+// Error specifies errors returned during packfile parsing.
+type Error struct {
+	reason, details string
+}
+
+// NewError returns a new error.
+func NewError(reason string) *Error {
+	return &Error{reason: reason}
+}
+
+// Error returns a text representation of the error.
+func (e *Error) Error() string {
+	if e.details == "" {
+		return e.reason
+	}
+
+	return fmt.Sprintf("%s: %s", e.reason, e.details)
+}
+
+// AddDetails adds details to an error, with additional text.
+func (e *Error) AddDetails(format string, args ...interface{}) *Error {
+	return &Error{
+		reason:  e.reason,
+		details: fmt.Sprintf(format, args...),
+	}
+}

vendor/gopkg.in/src-d/go-git.v4/plumbing/format/packfile/fsobject.go

@@ -0,0 +1,116 @@
+package packfile
+
+import (
+	"io"
+
+	billy "gopkg.in/src-d/go-billy.v4"
+	"gopkg.in/src-d/go-git.v4/plumbing"
+	"gopkg.in/src-d/go-git.v4/plumbing/cache"
+	"gopkg.in/src-d/go-git.v4/plumbing/format/idxfile"
+)
+
+// FSObject is an object from the packfile on the filesystem.
+type FSObject struct {
+	hash   plumbing.Hash
+	h      *ObjectHeader
+	offset int64
+	size   int64
+	typ    plumbing.ObjectType
+	index  idxfile.Index
+	fs     billy.Filesystem
+	path   string
+	cache  cache.Object
+}
+
+// NewFSObject creates a new filesystem object.
+func NewFSObject(
+	hash plumbing.Hash,
+	finalType plumbing.ObjectType,
+	offset int64,
+	contentSize int64,
+	index idxfile.Index,
+	fs billy.Filesystem,
+	path string,
+	cache cache.Object,
+) *FSObject {
+	return &FSObject{
+		hash:   hash,
+		offset: offset,
+		size:   contentSize,
+		typ:    finalType,
+		index:  index,
+		fs:     fs,
+		path:   path,
+		cache:  cache,
+	}
+}
+
+// Reader implements the plumbing.EncodedObject interface.
+func (o *FSObject) Reader() (io.ReadCloser, error) {
+	obj, ok := o.cache.Get(o.hash)
+	if ok && obj != o {
+		reader, err := obj.Reader()
+		if err != nil {
+			return nil, err
+		}
+
+		return reader, nil
+	}
+
+	f, err := o.fs.Open(o.path)
+	if err != nil {
+		return nil, err
+	}
+
+	p := NewPackfileWithCache(o.index, nil, f, o.cache)
+	r, err := p.getObjectContent(o.offset)
+	if err != nil {
+		_ = f.Close()
+		return nil, err
+	}
+
+	if err := f.Close(); err != nil {
+		return nil, err
+	}
+
+	return r, nil
+}
+
+// SetSize implements the plumbing.EncodedObject interface. This method
+// is a noop.
+func (o *FSObject) SetSize(int64) {}
+
+// SetType implements the plumbing.EncodedObject interface. This method is
+// a noop.
+func (o *FSObject) SetType(plumbing.ObjectType) {}
+
+// Hash implements the plumbing.EncodedObject interface.
+func (o *FSObject) Hash() plumbing.Hash { return o.hash }
+
+// Size implements the plumbing.EncodedObject interface.
+func (o *FSObject) Size() int64 { return o.size }
+
+// Type implements the plumbing.EncodedObject interface.
+func (o *FSObject) Type() plumbing.ObjectType {
+	return o.typ
+}
+
+// Writer implements the plumbing.EncodedObject interface. This method always
+// returns a nil writer.
+func (o *FSObject) Writer() (io.WriteCloser, error) {
+	return nil, nil
+}
+
+type objectReader struct {
+	io.ReadCloser
+	f billy.File
+}
+
+func (r *objectReader) Close() error {
+	if err := r.ReadCloser.Close(); err != nil {
+		_ = r.f.Close()
+		return err
+	}
+
+	return r.f.Close()
+}

vendor/gopkg.in/src-d/go-git.v4/plumbing/format/packfile/object_pack.go

@@ -0,0 +1,164 @@
+package packfile
+
+import (
+	"gopkg.in/src-d/go-git.v4/plumbing"
+)
+
+// ObjectToPack is a representation of an object that is going to be into a
+// pack file.
+type ObjectToPack struct {
+	// The main object to pack, it could be any object, including deltas
+	Object plumbing.EncodedObject
+	// Base is the object that a delta is based on (it could be also another delta).
+	// If the main object is not a delta, Base will be null
+	Base *ObjectToPack
+	// Original is the object that we can generate applying the delta to
+	// Base, or the same object as Object in the case of a non-delta
+	// object.
+	Original plumbing.EncodedObject
+	// Depth is the amount of deltas needed to resolve to obtain Original
+	// (delta based on delta based on ...)
+	Depth int
+
+	// offset in pack when object has been already written, or 0 if it
+	// has not been written yet
+	Offset int64
+
+	// Information from the original object
+	resolvedOriginal bool
+	originalType     plumbing.ObjectType
+	originalSize     int64
+	originalHash     plumbing.Hash
+}
+
+// newObjectToPack creates a correct ObjectToPack based on a non-delta object
+func newObjectToPack(o plumbing.EncodedObject) *ObjectToPack {
+	return &ObjectToPack{
+		Object:   o,
+		Original: o,
+	}
+}
+
+// newDeltaObjectToPack creates a correct ObjectToPack for a delta object, based on
+// his base (could be another delta), the delta target (in this case called original),
+// and the delta Object itself
+func newDeltaObjectToPack(base *ObjectToPack, original, delta plumbing.EncodedObject) *ObjectToPack {
+	return &ObjectToPack{
+		Object:   delta,
+		Base:     base,
+		Original: original,
+		Depth:    base.Depth + 1,
+	}
+}
+
+// BackToOriginal converts that ObjectToPack to a non-deltified object if it was one
+func (o *ObjectToPack) BackToOriginal() {
+	if o.IsDelta() && o.Original != nil {
+		o.Object = o.Original
+		o.Base = nil
+		o.Depth = 0
+	}
+}
+
+// IsWritten returns if that ObjectToPack was
+// already written into the packfile or not
+func (o *ObjectToPack) IsWritten() bool {
+	return o.Offset > 1
+}
+
+// MarkWantWrite marks this ObjectToPack as WantWrite
+// to avoid delta chain loops
+func (o *ObjectToPack) MarkWantWrite() {
+	o.Offset = 1
+}
+
+// WantWrite checks if this ObjectToPack was marked as WantWrite before
+func (o *ObjectToPack) WantWrite() bool {
+	return o.Offset == 1
+}
+
+// SetOriginal sets both Original and saves size, type and hash. If object
+// is nil Original is set but previous resolved values are kept
+func (o *ObjectToPack) SetOriginal(obj plumbing.EncodedObject) {
+	o.Original = obj
+	o.SaveOriginalMetadata()
+}
+
+// SaveOriginalMetadata saves size, type and hash of Original object
+func (o *ObjectToPack) SaveOriginalMetadata() {
+	if o.Original != nil {
+		o.originalSize = o.Original.Size()
+		o.originalType = o.Original.Type()
+		o.originalHash = o.Original.Hash()
+		o.resolvedOriginal = true
+	}
+}
+
+// CleanOriginal sets Original to nil
+func (o *ObjectToPack) CleanOriginal() {
+	o.Original = nil
+}
+
+func (o *ObjectToPack) Type() plumbing.ObjectType {
+	if o.Original != nil {
+		return o.Original.Type()
+	}
+
+	if o.resolvedOriginal {
+		return o.originalType
+	}
+
+	if o.Base != nil {
+		return o.Base.Type()
+	}
+
+	if o.Object != nil {
+		return o.Object.Type()
+	}
+
+	panic("cannot get type")
+}
+
+func (o *ObjectToPack) Hash() plumbing.Hash {
+	if o.Original != nil {
+		return o.Original.Hash()
+	}
+
+	if o.resolvedOriginal {
+		return o.originalHash
+	}
+
+	do, ok := o.Object.(plumbing.DeltaObject)
+	if ok {
+		return do.ActualHash()
+	}
+
+	panic("cannot get hash")
+}
+
+func (o *ObjectToPack) Size() int64 {
+	if o.Original != nil {
+		return o.Original.Size()
+	}
+
+	if o.resolvedOriginal {
+		return o.originalSize
+	}
+
+	do, ok := o.Object.(plumbing.DeltaObject)
+	if ok {
+		return do.ActualSize()
+	}
+
+	panic("cannot get ObjectToPack size")
+}
+
+func (o *ObjectToPack) IsDelta() bool {
+	return o.Base != nil
+}
+
+func (o *ObjectToPack) SetDelta(base *ObjectToPack, delta plumbing.EncodedObject) {
+	o.Object = delta
+	o.Base = base
+	o.Depth = base.Depth + 1
+}

vendor/gopkg.in/src-d/go-git.v4/plumbing/format/packfile/packfile.go

@@ -0,0 +1,487 @@
+package packfile
+
+import (
+	"bytes"
+	"io"
+	"os"
+
+	billy "gopkg.in/src-d/go-billy.v4"
+	"gopkg.in/src-d/go-git.v4/plumbing"
+	"gopkg.in/src-d/go-git.v4/plumbing/cache"
+	"gopkg.in/src-d/go-git.v4/plumbing/format/idxfile"
+	"gopkg.in/src-d/go-git.v4/plumbing/storer"
+)
+
+var (
+	// ErrInvalidObject is returned by Decode when an invalid object is
+	// found in the packfile.
+	ErrInvalidObject = NewError("invalid git object")
+	// ErrZLib is returned by Decode when there was an error unzipping
+	// the packfile contents.
+	ErrZLib = NewError("zlib reading error")
+)
+
+// When reading small objects from packfile it is beneficial to do so at
+// once to exploit the buffered I/O. In many cases the objects are so small
+// that they were already loaded to memory when the object header was
+// loaded from the packfile. Wrapping in FSObject would cause this buffered
+// data to be thrown away and then re-read later, with the additional
+// seeking causing reloads from disk. Objects smaller than this threshold
+// are now always read into memory and stored in cache instead of being
+// wrapped in FSObject.
+const smallObjectThreshold = 16 * 1024
+
+// Packfile allows retrieving information from inside a packfile.
+type Packfile struct {
+	idxfile.Index
+	fs             billy.Filesystem
+	file           billy.File
+	s              *Scanner
+	deltaBaseCache cache.Object
+	offsetToType   map[int64]plumbing.ObjectType
+}
+
+// NewPackfileWithCache creates a new Packfile with the given object cache.
+// If the filesystem is provided, the packfile will return FSObjects, otherwise
+// it will return MemoryObjects.
+func NewPackfileWithCache(
+	index idxfile.Index,
+	fs billy.Filesystem,
+	file billy.File,
+	cache cache.Object,
+) *Packfile {
+	s := NewScanner(file)
+	return &Packfile{
+		index,
+		fs,
+		file,
+		s,
+		cache,
+		make(map[int64]plumbing.ObjectType),
+	}
+}
+
+// NewPackfile returns a packfile representation for the given packfile file
+// and packfile idx.
+// If the filesystem is provided, the packfile will return FSObjects, otherwise
+// it will return MemoryObjects.
+func NewPackfile(index idxfile.Index, fs billy.Filesystem, file billy.File) *Packfile {
+	return NewPackfileWithCache(index, fs, file, cache.NewObjectLRUDefault())
+}
+
+// Get retrieves the encoded object in the packfile with the given hash.
+func (p *Packfile) Get(h plumbing.Hash) (plumbing.EncodedObject, error) {
+	offset, err := p.FindOffset(h)
+	if err != nil {
+		return nil, err
+	}
+
+	return p.GetByOffset(offset)
+}
+
+// GetByOffset retrieves the encoded object from the packfile with the given
+// offset.
+func (p *Packfile) GetByOffset(o int64) (plumbing.EncodedObject, error) {
+	hash, err := p.FindHash(o)
+	if err == nil {
+		if obj, ok := p.deltaBaseCache.Get(hash); ok {
+			return obj, nil
+		}
+	}
+
+	return p.objectAtOffset(o)
+}
+
+// GetSizeByOffset retrieves the size of the encoded object from the
+// packfile with the given offset.
+func (p *Packfile) GetSizeByOffset(o int64) (size int64, err error) {
+	if _, err := p.s.SeekFromStart(o); err != nil {
+		if err == io.EOF || isInvalid(err) {
+			return 0, plumbing.ErrObjectNotFound
+		}
+
+		return 0, err
+	}
+
+	h, err := p.nextObjectHeader()
+	if err != nil {
+		return 0, err
+	}
+	return p.getObjectSize(h)
+}
+
+func (p *Packfile) objectHeaderAtOffset(offset int64) (*ObjectHeader, error) {
+	h, err := p.s.SeekObjectHeader(offset)
+	p.s.pendingObject = nil
+	return h, err
+}
+
+func (p *Packfile) nextObjectHeader() (*ObjectHeader, error) {
+	h, err := p.s.NextObjectHeader()
+	p.s.pendingObject = nil
+	return h, err
+}
+
+func (p *Packfile) getObjectSize(h *ObjectHeader) (int64, error) {
+	switch h.Type {
+	case plumbing.CommitObject, plumbing.TreeObject, plumbing.BlobObject, plumbing.TagObject:
+		return h.Length, nil
+	case plumbing.REFDeltaObject, plumbing.OFSDeltaObject:
+		buf := bufPool.Get().(*bytes.Buffer)
+		buf.Reset()
+		defer bufPool.Put(buf)
+
+		if _, _, err := p.s.NextObject(buf); err != nil {
+			return 0, err
+		}
+
+		delta := buf.Bytes()
+		_, delta = decodeLEB128(delta) // skip src size
+		sz, _ := decodeLEB128(delta)
+		return int64(sz), nil
+	default:
+		return 0, ErrInvalidObject.AddDetails("type %q", h.Type)
+	}
+}
+
+func (p *Packfile) getObjectType(h *ObjectHeader) (typ plumbing.ObjectType, err error) {
+	switch h.Type {
+	case plumbing.CommitObject, plumbing.TreeObject, plumbing.BlobObject, plumbing.TagObject:
+		return h.Type, nil
+	case plumbing.REFDeltaObject, plumbing.OFSDeltaObject:
+		var offset int64
+		if h.Type == plumbing.REFDeltaObject {
+			offset, err = p.FindOffset(h.Reference)
+			if err != nil {
+				return
+			}
+		} else {
+			offset = h.OffsetReference
+		}
+
+		if baseType, ok := p.offsetToType[offset]; ok {
+			typ = baseType
+		} else {
+			h, err = p.objectHeaderAtOffset(offset)
+			if err != nil {
+				return
+			}
+
+			typ, err = p.getObjectType(h)
+			if err != nil {
+				return
+			}
+		}
+	default:
+		err = ErrInvalidObject.AddDetails("type %q", h.Type)
+	}
+
+	return
+}
+
+func (p *Packfile) objectAtOffset(offset int64) (plumbing.EncodedObject, error) {
+	h, err := p.objectHeaderAtOffset(offset)
+	if err != nil {
+		if err == io.EOF || isInvalid(err) {
+			return nil, plumbing.ErrObjectNotFound
+		}
+		return nil, err
+	}
+
+	// If we have no filesystem, we will return a MemoryObject instead
+	// of an FSObject.
+	if p.fs == nil {
+		return p.getNextObject(h)
+	}
+
+	// If the object is not a delta and it's small enough then read it
+	// completely into memory now since it is already read from disk
+	// into buffer anyway.
+	if h.Length <= smallObjectThreshold && h.Type != plumbing.OFSDeltaObject && h.Type != plumbing.REFDeltaObject {
+		return p.getNextObject(h)
+	}
+
+	hash, err := p.FindHash(h.Offset)
+	if err != nil {
+		return nil, err
+	}
+
+	size, err := p.getObjectSize(h)
+	if err != nil {
+		return nil, err
+	}
+
+	typ, err := p.getObjectType(h)
+	if err != nil {
+		return nil, err
+	}
+
+	p.offsetToType[h.Offset] = typ
+
+	return NewFSObject(
+		hash,
+		typ,
+		h.Offset,
+		size,
+		p.Index,
+		p.fs,
+		p.file.Name(),
+		p.deltaBaseCache,
+	), nil
+}
+
+func (p *Packfile) getObjectContent(offset int64) (io.ReadCloser, error) {
+	ref, err := p.FindHash(offset)
+	if err == nil {
+		obj, ok := p.cacheGet(ref)
+		if ok {
+			reader, err := obj.Reader()
+			if err != nil {
+				return nil, err
+			}
+
+			return reader, nil
+		}
+	}
+
+	h, err := p.objectHeaderAtOffset(offset)
+	if err != nil {
+		return nil, err
+	}
+
+	obj, err := p.getNextObject(h)
+	if err != nil {
+		return nil, err
+	}
+
+	return obj.Reader()
+}
+
+func (p *Packfile) getNextObject(h *ObjectHeader) (plumbing.EncodedObject, error) {
+	var obj = new(plumbing.MemoryObject)
+	obj.SetSize(h.Length)
+	obj.SetType(h.Type)
+
+	var err error
+	switch h.Type {
+	case plumbing.CommitObject, plumbing.TreeObject, plumbing.BlobObject, plumbing.TagObject:
+		err = p.fillRegularObjectContent(obj)
+	case plumbing.REFDeltaObject:
+		err = p.fillREFDeltaObjectContent(obj, h.Reference)
+	case plumbing.OFSDeltaObject:
+		err = p.fillOFSDeltaObjectContent(obj, h.OffsetReference)
+	default:
+		err = ErrInvalidObject.AddDetails("type %q", h.Type)
+	}
+
+	if err != nil {
+		return nil, err
+	}
+
+	return obj, nil
+}
+
+func (p *Packfile) fillRegularObjectContent(obj plumbing.EncodedObject) error {
+	w, err := obj.Writer()
+	if err != nil {
+		return err
+	}
+
+	_, _, err = p.s.NextObject(w)
+	p.cachePut(obj)
+
+	return err
+}
+
+func (p *Packfile) fillREFDeltaObjectContent(obj plumbing.EncodedObject, ref plumbing.Hash) error {
+	buf := bufPool.Get().(*bytes.Buffer)
+	buf.Reset()
+	_, _, err := p.s.NextObject(buf)
+	if err != nil {
+		return err
+	}
+
+	base, ok := p.cacheGet(ref)
+	if !ok {
+		base, err = p.Get(ref)
+		if err != nil {
+			return err
+		}
+	}
+
+	obj.SetType(base.Type())
+	err = ApplyDelta(obj, base, buf.Bytes())
+	p.cachePut(obj)
+	bufPool.Put(buf)
+
+	return err
+}
+
+func (p *Packfile) fillOFSDeltaObjectContent(obj plumbing.EncodedObject, offset int64) error {
+	buf := bytes.NewBuffer(nil)
+	_, _, err := p.s.NextObject(buf)
+	if err != nil {
+		return err
+	}
+
+	var base plumbing.EncodedObject
+	var ok bool
+	hash, err := p.FindHash(offset)
+	if err == nil {
+		base, ok = p.cacheGet(hash)
+	}
+
+	if !ok {
+		base, err = p.GetByOffset(offset)
+		if err != nil {
+			return err
+		}
+	}
+
+	obj.SetType(base.Type())
+	err = ApplyDelta(obj, base, buf.Bytes())
+	p.cachePut(obj)
+
+	return err
+}
+
+func (p *Packfile) cacheGet(h plumbing.Hash) (plumbing.EncodedObject, bool) {
+	if p.deltaBaseCache == nil {
+		return nil, false
+	}
+
+	return p.deltaBaseCache.Get(h)
+}
+
+func (p *Packfile) cachePut(obj plumbing.EncodedObject) {
+	if p.deltaBaseCache == nil {
+		return
+	}
+
+	p.deltaBaseCache.Put(obj)
+}
+
+// GetAll returns an iterator with all encoded objects in the packfile.
+// The iterator returned is not thread-safe, it should be used in the same
+// thread as the Packfile instance.
+func (p *Packfile) GetAll() (storer.EncodedObjectIter, error) {
+	return p.GetByType(plumbing.AnyObject)
+}
+
+// GetByType returns all the objects of the given type.
+func (p *Packfile) GetByType(typ plumbing.ObjectType) (storer.EncodedObjectIter, error) {
+	switch typ {
+	case plumbing.AnyObject,
+		plumbing.BlobObject,
+		plumbing.TreeObject,
+		plumbing.CommitObject,
+		plumbing.TagObject:
+		entries, err := p.EntriesByOffset()
+		if err != nil {
+			return nil, err
+		}
+
+		return &objectIter{
+			// Easiest way to provide an object decoder is just to pass a Packfile
+			// instance. To not mess with the seeks, it's a new instance with a
+			// different scanner but the same cache and offset to hash map for
+			// reusing as much cache as possible.
+			p:    p,
+			iter: entries,
+			typ:  typ,
+		}, nil
+	default:
+		return nil, plumbing.ErrInvalidType
+	}
+}
+
+// ID returns the ID of the packfile, which is the checksum at the end of it.
+func (p *Packfile) ID() (plumbing.Hash, error) {
+	prev, err := p.file.Seek(-20, io.SeekEnd)
+	if err != nil {
+		return plumbing.ZeroHash, err
+	}
+
+	var hash plumbing.Hash
+	if _, err := io.ReadFull(p.file, hash[:]); err != nil {
+		return plumbing.ZeroHash, err
+	}
+
+	if _, err := p.file.Seek(prev, io.SeekStart); err != nil {
+		return plumbing.ZeroHash, err
+	}
+
+	return hash, nil
+}
+
+// Close the packfile and its resources.
+func (p *Packfile) Close() error {
+	closer, ok := p.file.(io.Closer)
+	if !ok {
+		return nil
+	}
+
+	return closer.Close()
+}
+
+type objectIter struct {
+	p    *Packfile
+	typ  plumbing.ObjectType
+	iter idxfile.EntryIter
+}
+
+func (i *objectIter) Next() (plumbing.EncodedObject, error) {
+	for {
+		e, err := i.iter.Next()
+		if err != nil {
+			return nil, err
+		}
+
+		obj, err := i.p.GetByOffset(int64(e.Offset))
+		if err != nil {
+			return nil, err
+		}
+
+		if i.typ == plumbing.AnyObject || obj.Type() == i.typ {
+			return obj, nil
+		}
+	}
+}
+
+func (i *objectIter) ForEach(f func(plumbing.EncodedObject) error) error {
+	for {
+		o, err := i.Next()
+		if err != nil {
+			if err == io.EOF {
+				return nil
+			}
+			return err
+		}
+
+		if err := f(o); err != nil {
+			return err
+		}
+	}
+}
+
+func (i *objectIter) Close() {
+	i.iter.Close()
+}
+
+// isInvalid checks whether an error is an os.PathError with an os.ErrInvalid
+// error inside. It also checks for the windows error, which is different from
+// os.ErrInvalid.
+func isInvalid(err error) bool {
+	pe, ok := err.(*os.PathError)
+	if !ok {
+		return false
+	}
+
+	errstr := pe.Err.Error()
+	return errstr == errInvalidUnix || errstr == errInvalidWindows
+}
+
+// errInvalidWindows is the Windows equivalent to os.ErrInvalid
+const errInvalidWindows = "The parameter is incorrect."
+
+var errInvalidUnix = os.ErrInvalid.Error()

vendor/gopkg.in/src-d/go-git.v4/plumbing/format/packfile/parser.go

@@ -0,0 +1,483 @@
+package packfile
+
+import (
+	"bytes"
+	"errors"
+	"io"
+
+	"gopkg.in/src-d/go-git.v4/plumbing"
+	"gopkg.in/src-d/go-git.v4/plumbing/cache"
+	"gopkg.in/src-d/go-git.v4/plumbing/storer"
+)
+
+var (
+	// ErrReferenceDeltaNotFound is returned when the reference delta is not
+	// found.
+	ErrReferenceDeltaNotFound = errors.New("reference delta not found")
+
+	// ErrNotSeekableSource is returned when the source for the parser is not
+	// seekable and a storage was not provided, so it can't be parsed.
+	ErrNotSeekableSource = errors.New("parser source is not seekable and storage was not provided")
+
+	// ErrDeltaNotCached is returned when the delta could not be found in cache.
+	ErrDeltaNotCached = errors.New("delta could not be found in cache")
+)
+
+// Observer interface is implemented by index encoders.
+type Observer interface {
+	// OnHeader is called when a new packfile is opened.
+	OnHeader(count uint32) error
+	// OnInflatedObjectHeader is called for each object header read.
+	OnInflatedObjectHeader(t plumbing.ObjectType, objSize int64, pos int64) error
+	// OnInflatedObjectContent is called for each decoded object.
+	OnInflatedObjectContent(h plumbing.Hash, pos int64, crc uint32, content []byte) error
+	// OnFooter is called when decoding is done.
+	OnFooter(h plumbing.Hash) error
+}
+
+// Parser decodes a packfile and calls any observer associated to it. Is used
+// to generate indexes.
+type Parser struct {
+	storage    storer.EncodedObjectStorer
+	scanner    *Scanner
+	count      uint32
+	oi         []*objectInfo
+	oiByHash   map[plumbing.Hash]*objectInfo
+	oiByOffset map[int64]*objectInfo
+	hashOffset map[plumbing.Hash]int64
+	checksum   plumbing.Hash
+
+	cache *cache.BufferLRU
+	// delta content by offset, only used if source is not seekable
+	deltas map[int64][]byte
+
+	ob []Observer
+}
+
+// NewParser creates a new Parser. The Scanner source must be seekable.
+// If it's not, NewParserWithStorage should be used instead.
+func NewParser(scanner *Scanner, ob ...Observer) (*Parser, error) {
+	return NewParserWithStorage(scanner, nil, ob...)
+}
+
+// NewParserWithStorage creates a new Parser. The scanner source must either
+// be seekable or a storage must be provided.
+func NewParserWithStorage(
+	scanner *Scanner,
+	storage storer.EncodedObjectStorer,
+	ob ...Observer,
+) (*Parser, error) {
+	if !scanner.IsSeekable && storage == nil {
+		return nil, ErrNotSeekableSource
+	}
+
+	var deltas map[int64][]byte
+	if !scanner.IsSeekable {
+		deltas = make(map[int64][]byte)
+	}
+
+	return &Parser{
+		storage: storage,
+		scanner: scanner,
+		ob:      ob,
+		count:   0,
+		cache:   cache.NewBufferLRUDefault(),
+		deltas:  deltas,
+	}, nil
+}
+
+func (p *Parser) forEachObserver(f func(o Observer) error) error {
+	for _, o := range p.ob {
+		if err := f(o); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (p *Parser) onHeader(count uint32) error {
+	return p.forEachObserver(func(o Observer) error {
+		return o.OnHeader(count)
+	})
+}
+
+func (p *Parser) onInflatedObjectHeader(
+	t plumbing.ObjectType,
+	objSize int64,
+	pos int64,
+) error {
+	return p.forEachObserver(func(o Observer) error {
+		return o.OnInflatedObjectHeader(t, objSize, pos)
+	})
+}
+
+func (p *Parser) onInflatedObjectContent(
+	h plumbing.Hash,
+	pos int64,
+	crc uint32,
+	content []byte,
+) error {
+	return p.forEachObserver(func(o Observer) error {
+		return o.OnInflatedObjectContent(h, pos, crc, content)
+	})
+}
+
+func (p *Parser) onFooter(h plumbing.Hash) error {
+	return p.forEachObserver(func(o Observer) error {
+		return o.OnFooter(h)
+	})
+}
+
+// Parse start decoding phase of the packfile.
+func (p *Parser) Parse() (plumbing.Hash, error) {
+	if err := p.init(); err != nil {
+		return plumbing.ZeroHash, err
+	}
+
+	if err := p.indexObjects(); err != nil {
+		return plumbing.ZeroHash, err
+	}
+
+	var err error
+	p.checksum, err = p.scanner.Checksum()
+	if err != nil && err != io.EOF {
+		return plumbing.ZeroHash, err
+	}
+
+	if err := p.resolveDeltas(); err != nil {
+		return plumbing.ZeroHash, err
+	}
+
+	if err := p.onFooter(p.checksum); err != nil {
+		return plumbing.ZeroHash, err
+	}
+
+	return p.checksum, nil
+}
+
+func (p *Parser) init() error {
+	_, c, err := p.scanner.Header()
+	if err != nil {
+		return err
+	}
+
+	if err := p.onHeader(c); err != nil {
+		return err
+	}
+
+	p.count = c
+	p.oiByHash = make(map[plumbing.Hash]*objectInfo, p.count)
+	p.oiByOffset = make(map[int64]*objectInfo, p.count)
+	p.oi = make([]*objectInfo, p.count)
+
+	return nil
+}
+
+func (p *Parser) indexObjects() error {
+	buf := new(bytes.Buffer)
+
+	for i := uint32(0); i < p.count; i++ {
+		buf.Reset()
+
+		oh, err := p.scanner.NextObjectHeader()
+		if err != nil {
+			return err
+		}
+
+		delta := false
+		var ota *objectInfo
+		switch t := oh.Type; t {
+		case plumbing.OFSDeltaObject:
+			delta = true
+
+			parent, ok := p.oiByOffset[oh.OffsetReference]
+			if !ok {
+				return plumbing.ErrObjectNotFound
+			}
+
+			ota = newDeltaObject(oh.Offset, oh.Length, t, parent)
+			parent.Children = append(parent.Children, ota)
+		case plumbing.REFDeltaObject:
+			delta = true
+			parent, ok := p.oiByHash[oh.Reference]
+			if !ok {
+				// can't find referenced object in this pack file
+				// this must be a "thin" pack.
+				parent = &objectInfo{ //Placeholder parent
+					SHA1:        oh.Reference,
+					ExternalRef: true, // mark as an external reference that must be resolved
+					Type:        plumbing.AnyObject,
+					DiskType:    plumbing.AnyObject,
+				}
+				p.oiByHash[oh.Reference] = parent
+			}
+			ota = newDeltaObject(oh.Offset, oh.Length, t, parent)
+			parent.Children = append(parent.Children, ota)
+
+		default:
+			ota = newBaseObject(oh.Offset, oh.Length, t)
+		}
+
+		_, crc, err := p.scanner.NextObject(buf)
+		if err != nil {
+			return err
+		}
+
+		ota.Crc32 = crc
+		ota.Length = oh.Length
+
+		data := buf.Bytes()
+		if !delta {
+			sha1, err := getSHA1(ota.Type, data)
+			if err != nil {
+				return err
+			}
+
+			ota.SHA1 = sha1
+			p.oiByHash[ota.SHA1] = ota
+		}
+
+		if p.storage != nil && !delta {
+			obj := new(plumbing.MemoryObject)
+			obj.SetSize(oh.Length)
+			obj.SetType(oh.Type)
+			if _, err := obj.Write(data); err != nil {
+				return err
+			}
+
+			if _, err := p.storage.SetEncodedObject(obj); err != nil {
+				return err
+			}
+		}
+
+		if delta && !p.scanner.IsSeekable {
+			p.deltas[oh.Offset] = make([]byte, len(data))
+			copy(p.deltas[oh.Offset], data)
+		}
+
+		p.oiByOffset[oh.Offset] = ota
+		p.oi[i] = ota
+	}
+
+	return nil
+}
+
+func (p *Parser) resolveDeltas() error {
+	for _, obj := range p.oi {
+		content, err := p.get(obj)
+		if err != nil {
+			return err
+		}
+
+		if err := p.onInflatedObjectHeader(obj.Type, obj.Length, obj.Offset); err != nil {
+			return err
+		}
+
+		if err := p.onInflatedObjectContent(obj.SHA1, obj.Offset, obj.Crc32, content); err != nil {
+			return err
+		}
+
+		if !obj.IsDelta() && len(obj.Children) > 0 {
+			for _, child := range obj.Children {
+				if _, err := p.resolveObject(child, content); err != nil {
+					return err
+				}
+			}
+
+			// Remove the delta from the cache.
+			if obj.DiskType.IsDelta() && !p.scanner.IsSeekable {
+				delete(p.deltas, obj.Offset)
+			}
+		}
+	}
+
+	return nil
+}
+
+func (p *Parser) get(o *objectInfo) (b []byte, err error) {
+	var ok bool
+	if !o.ExternalRef { // skip cache check for placeholder parents
+		b, ok = p.cache.Get(o.Offset)
+	}
+
+	// If it's not on the cache and is not a delta we can try to find it in the
+	// storage, if there's one. External refs must enter here.
+	if !ok && p.storage != nil && !o.Type.IsDelta() {
+		e, err := p.storage.EncodedObject(plumbing.AnyObject, o.SHA1)
+		if err != nil {
+			return nil, err
+		}
+		o.Type = e.Type()
+
+		r, err := e.Reader()
+		if err != nil {
+			return nil, err
+		}
+
+		b = make([]byte, e.Size())
+		if _, err = r.Read(b); err != nil {
+			return nil, err
+		}
+	}
+
+	if b != nil {
+		return b, nil
+	}
+
+	if o.ExternalRef {
+		// we were not able to resolve a ref in a thin pack
+		return nil, ErrReferenceDeltaNotFound
+	}
+
+	var data []byte
+	if o.DiskType.IsDelta() {
+		base, err := p.get(o.Parent)
+		if err != nil {
+			return nil, err
+		}
+
+		data, err = p.resolveObject(o, base)
+		if err != nil {
+			return nil, err
+		}
+	} else {
+		data, err = p.readData(o)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	if len(o.Children) > 0 {
+		p.cache.Put(o.Offset, data)
+	}
+
+	return data, nil
+}
+
+func (p *Parser) resolveObject(
+	o *objectInfo,
+	base []byte,
+) ([]byte, error) {
+	if !o.DiskType.IsDelta() {
+		return nil, nil
+	}
+
+	data, err := p.readData(o)
+	if err != nil {
+		return nil, err
+	}
+
+	data, err = applyPatchBase(o, data, base)
+	if err != nil {
+		return nil, err
+	}
+
+	if p.storage != nil {
+		obj := new(plumbing.MemoryObject)
+		obj.SetSize(o.Size())
+		obj.SetType(o.Type)
+		if _, err := obj.Write(data); err != nil {
+			return nil, err
+		}
+
+		if _, err := p.storage.SetEncodedObject(obj); err != nil {
+			return nil, err
+		}
+	}
+
+	return data, nil
+}
+
+func (p *Parser) readData(o *objectInfo) ([]byte, error) {
+	if !p.scanner.IsSeekable && o.DiskType.IsDelta() {
+		data, ok := p.deltas[o.Offset]
+		if !ok {
+			return nil, ErrDeltaNotCached
+		}
+
+		return data, nil
+	}
+
+	if _, err := p.scanner.SeekObjectHeader(o.Offset); err != nil {
+		return nil, err
+	}
+
+	buf := new(bytes.Buffer)
+	if _, _, err := p.scanner.NextObject(buf); err != nil {
+		return nil, err
+	}
+
+	return buf.Bytes(), nil
+}
+
+func applyPatchBase(ota *objectInfo, data, base []byte) ([]byte, error) {
+	patched, err := PatchDelta(base, data)
+	if err != nil {
+		return nil, err
+	}
+
+	if ota.SHA1 == plumbing.ZeroHash {
+		ota.Type = ota.Parent.Type
+		sha1, err := getSHA1(ota.Type, patched)
+		if err != nil {
+			return nil, err
+		}
+
+		ota.SHA1 = sha1
+		ota.Length = int64(len(patched))
+	}
+
+	return patched, nil
+}
+
+func getSHA1(t plumbing.ObjectType, data []byte) (plumbing.Hash, error) {
+	hasher := plumbing.NewHasher(t, int64(len(data)))
+	if _, err := hasher.Write(data); err != nil {
+		return plumbing.ZeroHash, err
+	}
+
+	return hasher.Sum(), nil
+}
+
+type objectInfo struct {
+	Offset      int64
+	Length      int64
+	Type        plumbing.ObjectType
+	DiskType    plumbing.ObjectType
+	ExternalRef bool // indicates this is an external reference in a thin pack file
+
+	Crc32 uint32
+
+	Parent   *objectInfo
+	Children []*objectInfo
+	SHA1     plumbing.Hash
+}
+
+func newBaseObject(offset, length int64, t plumbing.ObjectType) *objectInfo {
+	return newDeltaObject(offset, length, t, nil)
+}
+
+func newDeltaObject(
+	offset, length int64,
+	t plumbing.ObjectType,
+	parent *objectInfo,
+) *objectInfo {
+	obj := &objectInfo{
+		Offset:   offset,
+		Length:   length,
+		Type:     t,
+		DiskType: t,
+		Crc32:    0,
+		Parent:   parent,
+	}
+
+	return obj
+}
+
+func (o *objectInfo) IsDelta() bool {
+	return o.Type.IsDelta()
+}
+
+func (o *objectInfo) Size() int64 {
+	return o.Length
+}

vendor/gopkg.in/src-d/go-git.v4/plumbing/format/packfile/patch_delta.go

@@ -0,0 +1,229 @@
+package packfile
+
+import (
+	"errors"
+	"io/ioutil"
+
+	"gopkg.in/src-d/go-git.v4/plumbing"
+)
+
+// See https://github.com/git/git/blob/49fa3dc76179e04b0833542fa52d0f287a4955ac/delta.h
+// https://github.com/git/git/blob/c2c5f6b1e479f2c38e0e01345350620944e3527f/patch-delta.c,
+// and https://github.com/tarruda/node-git-core/blob/master/src/js/delta.js
+// for details about the delta format.
+
+const deltaSizeMin = 4
+
+// ApplyDelta writes to target the result of applying the modification deltas in delta to base.
+func ApplyDelta(target, base plumbing.EncodedObject, delta []byte) error {
+	r, err := base.Reader()
+	if err != nil {
+		return err
+	}
+
+	w, err := target.Writer()
+	if err != nil {
+		return err
+	}
+
+	src, err := ioutil.ReadAll(r)
+	if err != nil {
+		return err
+	}
+
+	dst, err := PatchDelta(src, delta)
+	if err != nil {
+		return err
+	}
+
+	target.SetSize(int64(len(dst)))
+
+	_, err = w.Write(dst)
+	return err
+}
+
+var (
+	ErrInvalidDelta = errors.New("invalid delta")
+	ErrDeltaCmd     = errors.New("wrong delta command")
+)
+
+// PatchDelta returns the result of applying the modification deltas in delta to src.
+// An error will be returned if delta is corrupted (ErrDeltaLen) or an action command
+// is not copy from source or copy from delta (ErrDeltaCmd).
+func PatchDelta(src, delta []byte) ([]byte, error) {
+	if len(delta) < deltaSizeMin {
+		return nil, ErrInvalidDelta
+	}
+
+	srcSz, delta := decodeLEB128(delta)
+	if srcSz != uint(len(src)) {
+		return nil, ErrInvalidDelta
+	}
+
+	targetSz, delta := decodeLEB128(delta)
+	remainingTargetSz := targetSz
+
+	var cmd byte
+	dest := make([]byte, 0, targetSz)
+	for {
+		if len(delta) == 0 {
+			return nil, ErrInvalidDelta
+		}
+
+		cmd = delta[0]
+		delta = delta[1:]
+		if isCopyFromSrc(cmd) {
+			var offset, sz uint
+			var err error
+			offset, delta, err = decodeOffset(cmd, delta)
+			if err != nil {
+				return nil, err
+			}
+
+			sz, delta, err = decodeSize(cmd, delta)
+			if err != nil {
+				return nil, err
+			}
+
+			if invalidSize(sz, targetSz) ||
+				invalidOffsetSize(offset, sz, srcSz) {
+				break
+			}
+			dest = append(dest, src[offset:offset+sz]...)
+			remainingTargetSz -= sz
+		} else if isCopyFromDelta(cmd) {
+			sz := uint(cmd) // cmd is the size itself
+			if invalidSize(sz, targetSz) {
+				return nil, ErrInvalidDelta
+			}
+
+			if uint(len(delta)) < sz {
+				return nil, ErrInvalidDelta
+			}
+
+			dest = append(dest, delta[0:sz]...)
+			remainingTargetSz -= sz
+			delta = delta[sz:]
+		} else {
+			return nil, ErrDeltaCmd
+		}
+
+		if remainingTargetSz <= 0 {
+			break
+		}
+	}
+
+	return dest, nil
+}
+
+// Decodes a number encoded as an unsigned LEB128 at the start of some
+// binary data and returns the decoded number and the rest of the
+// stream.
+//
+// This must be called twice on the delta data buffer, first to get the
+// expected source buffer size, and again to get the target buffer size.
+func decodeLEB128(input []byte) (uint, []byte) {
+	var num, sz uint
+	var b byte
+	for {
+		b = input[sz]
+		num |= (uint(b) & payload) << (sz * 7) // concats 7 bits chunks
+		sz++
+
+		if uint(b)&continuation == 0 || sz == uint(len(input)) {
+			break
+		}
+	}
+
+	return num, input[sz:]
+}
+
+const (
+	payload      = 0x7f // 0111 1111
+	continuation = 0x80 // 1000 0000
+)
+
+func isCopyFromSrc(cmd byte) bool {
+	return (cmd & 0x80) != 0
+}
+
+func isCopyFromDelta(cmd byte) bool {
+	return (cmd&0x80) == 0 && cmd != 0
+}
+
+func decodeOffset(cmd byte, delta []byte) (uint, []byte, error) {
+	var offset uint
+	if (cmd & 0x01) != 0 {
+		if len(delta) == 0 {
+			return 0, nil, ErrInvalidDelta
+		}
+		offset = uint(delta[0])
+		delta = delta[1:]
+	}
+	if (cmd & 0x02) != 0 {
+		if len(delta) == 0 {
+			return 0, nil, ErrInvalidDelta
+		}
+		offset |= uint(delta[0]) << 8
+		delta = delta[1:]
+	}
+	if (cmd & 0x04) != 0 {
+		if len(delta) == 0 {
+			return 0, nil, ErrInvalidDelta
+		}
+		offset |= uint(delta[0]) << 16
+		delta = delta[1:]
+	}
+	if (cmd & 0x08) != 0 {
+		if len(delta) == 0 {
+			return 0, nil, ErrInvalidDelta
+		}
+		offset |= uint(delta[0]) << 24
+		delta = delta[1:]
+	}
+
+	return offset, delta, nil
+}
+
+func decodeSize(cmd byte, delta []byte) (uint, []byte, error) {
+	var sz uint
+	if (cmd & 0x10) != 0 {
+		if len(delta) == 0 {
+			return 0, nil, ErrInvalidDelta
+		}
+		sz = uint(delta[0])
+		delta = delta[1:]
+	}
+	if (cmd & 0x20) != 0 {
+		if len(delta) == 0 {
+			return 0, nil, ErrInvalidDelta
+		}
+		sz |= uint(delta[0]) << 8
+		delta = delta[1:]
+	}
+	if (cmd & 0x40) != 0 {
+		if len(delta) == 0 {
+			return 0, nil, ErrInvalidDelta
+		}
+		sz |= uint(delta[0]) << 16
+		delta = delta[1:]
+	}
+	if sz == 0 {
+		sz = 0x10000
+	}
+
+	return sz, delta, nil
+}
+
+func invalidSize(sz, targetSz uint) bool {
+	return sz > targetSz
+}
+
+func invalidOffsetSize(offset, sz, srcSz uint) bool {
+	return sumOverflows(offset, sz) ||
+		offset+sz > srcSz
+}
+
+func sumOverflows(a, b uint) bool {
+	return a+b < a
+}

vendor/gopkg.in/src-d/go-git.v4/plumbing/format/packfile/scanner.go

@@ -0,0 +1,487 @@
+package packfile
+
+import (
+	"bufio"
+	"bytes"
+	"compress/zlib"
+	"fmt"
+	"hash"
+	"hash/crc32"
+	"io"
+	stdioutil "io/ioutil"
+	"sync"
+
+	"gopkg.in/src-d/go-git.v4/plumbing"
+	"gopkg.in/src-d/go-git.v4/utils/binary"
+	"gopkg.in/src-d/go-git.v4/utils/ioutil"
+)
+
+var (
+	// ErrEmptyPackfile is returned by ReadHeader when no data is found in the packfile
+	ErrEmptyPackfile = NewError("empty packfile")
+	// ErrBadSignature is returned by ReadHeader when the signature in the packfile is incorrect.
+	ErrBadSignature = NewError("malformed pack file signature")
+	// ErrUnsupportedVersion is returned by ReadHeader when the packfile version is
+	// different than VersionSupported.
+	ErrUnsupportedVersion = NewError("unsupported packfile version")
+	// ErrSeekNotSupported returned if seek is not support
+	ErrSeekNotSupported = NewError("not seek support")
+)
+
+// ObjectHeader contains the information related to the object, this information
+// is collected from the previous bytes to the content of the object.
+type ObjectHeader struct {
+	Type            plumbing.ObjectType
+	Offset          int64
+	Length          int64
+	Reference       plumbing.Hash
+	OffsetReference int64
+}
+
+type Scanner struct {
+	r   reader
+	zr  readerResetter
+	crc hash.Hash32
+
+	// pendingObject is used to detect if an object has been read, or still
+	// is waiting to be read
+	pendingObject    *ObjectHeader
+	version, objects uint32
+
+	// lsSeekable says if this scanner can do Seek or not, to have a Scanner
+	// seekable a r implementing io.Seeker is required
+	IsSeekable bool
+}
+
+// NewScanner returns a new Scanner based on a reader, if the given reader
+// implements io.ReadSeeker the Scanner will be also Seekable
+func NewScanner(r io.Reader) *Scanner {
+	seeker, ok := r.(io.ReadSeeker)
+	if !ok {
+		seeker = &trackableReader{Reader: r}
+	}
+
+	crc := crc32.NewIEEE()
+	return &Scanner{
+		r:          newTeeReader(newByteReadSeeker(seeker), crc),
+		crc:        crc,
+		IsSeekable: ok,
+	}
+}
+
+// Header reads the whole packfile header (signature, version and object count).
+// It returns the version and the object count and performs checks on the
+// validity of the signature and the version fields.
+func (s *Scanner) Header() (version, objects uint32, err error) {
+	if s.version != 0 {
+		return s.version, s.objects, nil
+	}
+
+	sig, err := s.readSignature()
+	if err != nil {
+		if err == io.EOF {
+			err = ErrEmptyPackfile
+		}
+
+		return
+	}
+
+	if !s.isValidSignature(sig) {
+		err = ErrBadSignature
+		return
+	}
+
+	version, err = s.readVersion()
+	s.version = version
+	if err != nil {
+		return
+	}
+
+	if !s.isSupportedVersion(version) {
+		err = ErrUnsupportedVersion.AddDetails("%d", version)
+		return
+	}
+
+	objects, err = s.readCount()
+	s.objects = objects
+	return
+}
+
+// readSignature reads an returns the signature field in the packfile.
+func (s *Scanner) readSignature() ([]byte, error) {
+	var sig = make([]byte, 4)
+	if _, err := io.ReadFull(s.r, sig); err != nil {
+		return []byte{}, err
+	}
+
+	return sig, nil
+}
+
+// isValidSignature returns if sig is a valid packfile signature.
+func (s *Scanner) isValidSignature(sig []byte) bool {
+	return bytes.Equal(sig, signature)
+}
+
+// readVersion reads and returns the version field of a packfile.
+func (s *Scanner) readVersion() (uint32, error) {
+	return binary.ReadUint32(s.r)
+}
+
+// isSupportedVersion returns whether version v is supported by the parser.
+// The current supported version is VersionSupported, defined above.
+func (s *Scanner) isSupportedVersion(v uint32) bool {
+	return v == VersionSupported
+}
+
+// readCount reads and returns the count of objects field of a packfile.
+func (s *Scanner) readCount() (uint32, error) {
+	return binary.ReadUint32(s.r)
+}
+
+// SeekObjectHeader seeks to specified offset and returns the ObjectHeader
+// for the next object in the reader
+func (s *Scanner) SeekObjectHeader(offset int64) (*ObjectHeader, error) {
+	// if seeking we assume that you are not interested in the header
+	if s.version == 0 {
+		s.version = VersionSupported
+	}
+
+	if _, err := s.r.Seek(offset, io.SeekStart); err != nil {
+		return nil, err
+	}
+
+	h, err := s.nextObjectHeader()
+	if err != nil {
+		return nil, err
+	}
+
+	h.Offset = offset
+	return h, nil
+}
+
+// NextObjectHeader returns the ObjectHeader for the next object in the reader
+func (s *Scanner) NextObjectHeader() (*ObjectHeader, error) {
+	if err := s.doPending(); err != nil {
+		return nil, err
+	}
+
+	offset, err := s.r.Seek(0, io.SeekCurrent)
+	if err != nil {
+		return nil, err
+	}
+
+	h, err := s.nextObjectHeader()
+	if err != nil {
+		return nil, err
+	}
+
+	h.Offset = offset
+	return h, nil
+}
+
+// nextObjectHeader returns the ObjectHeader for the next object in the reader
+// without the Offset field
+func (s *Scanner) nextObjectHeader() (*ObjectHeader, error) {
+	defer s.Flush()
+
+	s.crc.Reset()
+
+	h := &ObjectHeader{}
+	s.pendingObject = h
+
+	var err error
+	h.Offset, err = s.r.Seek(0, io.SeekCurrent)
+	if err != nil {
+		return nil, err
+	}
+
+	h.Type, h.Length, err = s.readObjectTypeAndLength()
+	if err != nil {
+		return nil, err
+	}
+
+	switch h.Type {
+	case plumbing.OFSDeltaObject:
+		no, err := binary.ReadVariableWidthInt(s.r)
+		if err != nil {
+			return nil, err
+		}
+
+		h.OffsetReference = h.Offset - no
+	case plumbing.REFDeltaObject:
+		var err error
+		h.Reference, err = binary.ReadHash(s.r)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	return h, nil
+}
+
+func (s *Scanner) doPending() error {
+	if s.version == 0 {
+		var err error
+		s.version, s.objects, err = s.Header()
+		if err != nil {
+			return err
+		}
+	}
+
+	return s.discardObjectIfNeeded()
+}
+
+func (s *Scanner) discardObjectIfNeeded() error {
+	if s.pendingObject == nil {
+		return nil
+	}
+
+	h := s.pendingObject
+	n, _, err := s.NextObject(stdioutil.Discard)
+	if err != nil {
+		return err
+	}
+
+	if n != h.Length {
+		return fmt.Errorf(
+			"error discarding object, discarded %d, expected %d",
+			n, h.Length,
+		)
+	}
+
+	return nil
+}
+
+// ReadObjectTypeAndLength reads and returns the object type and the
+// length field from an object entry in a packfile.
+func (s *Scanner) readObjectTypeAndLength() (plumbing.ObjectType, int64, error) {
+	t, c, err := s.readType()
+	if err != nil {
+		return t, 0, err
+	}
+
+	l, err := s.readLength(c)
+
+	return t, l, err
+}
+
+func (s *Scanner) readType() (plumbing.ObjectType, byte, error) {
+	var c byte
+	var err error
+	if c, err = s.r.ReadByte(); err != nil {
+		return plumbing.ObjectType(0), 0, err
+	}
+
+	typ := parseType(c)
+
+	return typ, c, nil
+}
+
+func parseType(b byte) plumbing.ObjectType {
+	return plumbing.ObjectType((b & maskType) >> firstLengthBits)
+}
+
+// the length is codified in the last 4 bits of the first byte and in
+// the last 7 bits of subsequent bytes.  Last byte has a 0 MSB.
+func (s *Scanner) readLength(first byte) (int64, error) {
+	length := int64(first & maskFirstLength)
+
+	c := first
+	shift := firstLengthBits
+	var err error
+	for c&maskContinue > 0 {
+		if c, err = s.r.ReadByte(); err != nil {
+			return 0, err
+		}
+
+		length += int64(c&maskLength) << shift
+		shift += lengthBits
+	}
+
+	return length, nil
+}
+
+// NextObject writes the content of the next object into the reader, returns
+// the number of bytes written, the CRC32 of the content and an error, if any
+func (s *Scanner) NextObject(w io.Writer) (written int64, crc32 uint32, err error) {
+	defer s.crc.Reset()
+
+	s.pendingObject = nil
+	written, err = s.copyObject(w)
+	s.Flush()
+	crc32 = s.crc.Sum32()
+	return
+}
+
+// ReadRegularObject reads and write a non-deltified object
+// from it zlib stream in an object entry in the packfile.
+func (s *Scanner) copyObject(w io.Writer) (n int64, err error) {
+	if s.zr == nil {
+		var zr io.ReadCloser
+		zr, err = zlib.NewReader(s.r)
+		if err != nil {
+			return 0, fmt.Errorf("zlib initialization error: %s", err)
+		}
+
+		s.zr = zr.(readerResetter)
+	} else {
+		if err = s.zr.Reset(s.r, nil); err != nil {
+			return 0, fmt.Errorf("zlib reset error: %s", err)
+		}
+	}
+
+	defer ioutil.CheckClose(s.zr, &err)
+	buf := byteSlicePool.Get().([]byte)
+	n, err = io.CopyBuffer(w, s.zr, buf)
+	byteSlicePool.Put(buf)
+	return
+}
+
+var byteSlicePool = sync.Pool{
+	New: func() interface{} {
+		return make([]byte, 32*1024)
+	},
+}
+
+// SeekFromStart sets a new offset from start, returns the old position before
+// the change.
+func (s *Scanner) SeekFromStart(offset int64) (previous int64, err error) {
+	// if seeking we assume that you are not interested in the header
+	if s.version == 0 {
+		s.version = VersionSupported
+	}
+
+	previous, err = s.r.Seek(0, io.SeekCurrent)
+	if err != nil {
+		return -1, err
+	}
+
+	_, err = s.r.Seek(offset, io.SeekStart)
+	return previous, err
+}
+
+// Checksum returns the checksum of the packfile
+func (s *Scanner) Checksum() (plumbing.Hash, error) {
+	err := s.discardObjectIfNeeded()
+	if err != nil {
+		return plumbing.ZeroHash, err
+	}
+
+	return binary.ReadHash(s.r)
+}
+
+// Close reads the reader until io.EOF
+func (s *Scanner) Close() error {
+	buf := byteSlicePool.Get().([]byte)
+	_, err := io.CopyBuffer(stdioutil.Discard, s.r, buf)
+	byteSlicePool.Put(buf)
+	return err
+}
+
+// Flush finishes writing the buffer to crc hasher in case we are using
+// a teeReader. Otherwise it is a no-op.
+func (s *Scanner) Flush() error {
+	tee, ok := s.r.(*teeReader)
+	if ok {
+		return tee.Flush()
+	}
+	return nil
+}
+
+type trackableReader struct {
+	count int64
+	io.Reader
+}
+
+// Read reads up to len(p) bytes into p.
+func (r *trackableReader) Read(p []byte) (n int, err error) {
+	n, err = r.Reader.Read(p)
+	r.count += int64(n)
+
+	return
+}
+
+// Seek only supports io.SeekCurrent, any other operation fails
+func (r *trackableReader) Seek(offset int64, whence int) (int64, error) {
+	if whence != io.SeekCurrent {
+		return -1, ErrSeekNotSupported
+	}
+
+	return r.count, nil
+}
+
+func newByteReadSeeker(r io.ReadSeeker) *bufferedSeeker {
+	return &bufferedSeeker{
+		r:      r,
+		Reader: *bufio.NewReader(r),
+	}
+}
+
+type bufferedSeeker struct {
+	r io.ReadSeeker
+	bufio.Reader
+}
+
+func (r *bufferedSeeker) Seek(offset int64, whence int) (int64, error) {
+	if whence == io.SeekCurrent && offset == 0 {
+		current, err := r.r.Seek(offset, whence)
+		if err != nil {
+			return current, err
+		}
+
+		return current - int64(r.Buffered()), nil
+	}
+
+	defer r.Reader.Reset(r.r)
+	return r.r.Seek(offset, whence)
+}
+
+type readerResetter interface {
+	io.ReadCloser
+	zlib.Resetter
+}
+
+type reader interface {
+	io.Reader
+	io.ByteReader
+	io.Seeker
+}
+
+type teeReader struct {
+	reader
+	w         hash.Hash32
+	bufWriter *bufio.Writer
+}
+
+func newTeeReader(r reader, h hash.Hash32) *teeReader {
+	return &teeReader{
+		reader:    r,
+		w:         h,
+		bufWriter: bufio.NewWriter(h),
+	}
+}
+
+func (r *teeReader) Read(p []byte) (n int, err error) {
+	r.Flush()
+
+	n, err = r.reader.Read(p)
+	if n > 0 {
+		if n, err := r.w.Write(p[:n]); err != nil {
+			return n, err
+		}
+	}
+	return
+}
+
+func (r *teeReader) ReadByte() (b byte, err error) {
+	b, err = r.reader.ReadByte()
+	if err == nil {
+		return b, r.bufWriter.WriteByte(b)
+	}
+
+	return
+}
+
+func (r *teeReader) Flush() (err error) {
+	return r.bufWriter.Flush()
+}

vendor/gopkg.in/src-d/go-git.v4/plumbing/format/pktline/encoder.go

@@ -0,0 +1,122 @@
+// Package pktline implements reading payloads form pkt-lines and encoding
+// pkt-lines from payloads.
+package pktline
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"io"
+)
+
+// An Encoder writes pkt-lines to an output stream.
+type Encoder struct {
+	w io.Writer
+}
+
+const (
+	// MaxPayloadSize is the maximum payload size of a pkt-line in bytes.
+	MaxPayloadSize = 65516
+
+	// For compatibility with canonical Git implementation, accept longer pkt-lines
+	OversizePayloadMax = 65520
+)
+
+var (
+	// FlushPkt are the contents of a flush-pkt pkt-line.
+	FlushPkt = []byte{'0', '0', '0', '0'}
+	// Flush is the payload to use with the Encode method to encode a flush-pkt.
+	Flush = []byte{}
+	// FlushString is the payload to use with the EncodeString method to encode a flush-pkt.
+	FlushString = ""
+	// ErrPayloadTooLong is returned by the Encode methods when any of the
+	// provided payloads is bigger than MaxPayloadSize.
+	ErrPayloadTooLong = errors.New("payload is too long")
+)
+
+// NewEncoder returns a new encoder that writes to w.
+func NewEncoder(w io.Writer) *Encoder {
+	return &Encoder{
+		w: w,
+	}
+}
+
+// Flush encodes a flush-pkt to the output stream.
+func (e *Encoder) Flush() error {
+	_, err := e.w.Write(FlushPkt)
+	return err
+}
+
+// Encode encodes a pkt-line with the payload specified and write it to
+// the output stream.  If several payloads are specified, each of them
+// will get streamed in their own pkt-lines.
+func (e *Encoder) Encode(payloads ...[]byte) error {
+	for _, p := range payloads {
+		if err := e.encodeLine(p); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func (e *Encoder) encodeLine(p []byte) error {
+	if len(p) > MaxPayloadSize {
+		return ErrPayloadTooLong
+	}
+
+	if bytes.Equal(p, Flush) {
+		return e.Flush()
+	}
+
+	n := len(p) + 4
+	if _, err := e.w.Write(asciiHex16(n)); err != nil {
+		return err
+	}
+	_, err := e.w.Write(p)
+	return err
+}
+
+// Returns the hexadecimal ascii representation of the 16 less
+// significant bits of n.  The length of the returned slice will always
+// be 4.  Example: if n is 1234 (0x4d2), the return value will be
+// []byte{'0', '4', 'd', '2'}.
+func asciiHex16(n int) []byte {
+	var ret [4]byte
+	ret[0] = byteToASCIIHex(byte(n & 0xf000 >> 12))
+	ret[1] = byteToASCIIHex(byte(n & 0x0f00 >> 8))
+	ret[2] = byteToASCIIHex(byte(n & 0x00f0 >> 4))
+	ret[3] = byteToASCIIHex(byte(n & 0x000f))
+
+	return ret[:]
+}
+
+// turns a byte into its hexadecimal ascii representation.  Example:
+// from 11 (0xb) to 'b'.
+func byteToASCIIHex(n byte) byte {
+	if n < 10 {
+		return '0' + n
+	}
+
+	return 'a' - 10 + n
+}
+
+// EncodeString works similarly as Encode but payloads are specified as strings.
+func (e *Encoder) EncodeString(payloads ...string) error {
+	for _, p := range payloads {
+		if err := e.Encode([]byte(p)); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+// Encodef encodes a single pkt-line with the payload formatted as
+// the format specifier. The rest of the arguments will be used in
+// the format string.
+func (e *Encoder) Encodef(format string, a ...interface{}) error {
+	return e.EncodeString(
+		fmt.Sprintf(format, a...),
+	)
+}

vendor/gopkg.in/src-d/go-git.v4/plumbing/format/pktline/scanner.go

@@ -0,0 +1,134 @@
+package pktline
+
+import (
+	"errors"
+	"io"
+)
+
+const (
+	lenSize = 4
+)
+
+// ErrInvalidPktLen is returned by Err() when an invalid pkt-len is found.
+var ErrInvalidPktLen = errors.New("invalid pkt-len found")
+
+// Scanner provides a convenient interface for reading the payloads of a
+// series of pkt-lines.  It takes an io.Reader providing the source,
+// which then can be tokenized through repeated calls to the Scan
+// method.
+//
+// After each Scan call, the Bytes method will return the payload of the
+// corresponding pkt-line on a shared buffer, which will be 65516 bytes
+// or smaller.  Flush pkt-lines are represented by empty byte slices.
+//
+// Scanning stops at EOF or the first I/O error.
+type Scanner struct {
+	r       io.Reader     // The reader provided by the client
+	err     error         // Sticky error
+	payload []byte        // Last pkt-payload
+	len     [lenSize]byte // Last pkt-len
+}
+
+// NewScanner returns a new Scanner to read from r.
+func NewScanner(r io.Reader) *Scanner {
+	return &Scanner{
+		r: r,
+	}
+}
+
+// Err returns the first error encountered by the Scanner.
+func (s *Scanner) Err() error {
+	return s.err
+}
+
+// Scan advances the Scanner to the next pkt-line, whose payload will
+// then be available through the Bytes method.  Scanning stops at EOF
+// or the first I/O error.  After Scan returns false, the Err method
+// will return any error that occurred during scanning, except that if
+// it was io.EOF, Err will return nil.
+func (s *Scanner) Scan() bool {
+	var l int
+	l, s.err = s.readPayloadLen()
+	if s.err == io.EOF {
+		s.err = nil
+		return false
+	}
+	if s.err != nil {
+		return false
+	}
+
+	if cap(s.payload) < l {
+		s.payload = make([]byte, 0, l)
+	}
+
+	if _, s.err = io.ReadFull(s.r, s.payload[:l]); s.err != nil {
+		return false
+	}
+	s.payload = s.payload[:l]
+
+	return true
+}
+
+// Bytes returns the most recent payload generated by a call to Scan.
+// The underlying array may point to data that will be overwritten by a
+// subsequent call to Scan. It does no allocation.
+func (s *Scanner) Bytes() []byte {
+	return s.payload
+}
+
+// Method readPayloadLen returns the payload length by reading the
+// pkt-len and subtracting the pkt-len size.
+func (s *Scanner) readPayloadLen() (int, error) {
+	if _, err := io.ReadFull(s.r, s.len[:]); err != nil {
+		if err == io.ErrUnexpectedEOF {
+			return 0, ErrInvalidPktLen
+		}
+
+		return 0, err
+	}
+
+	n, err := hexDecode(s.len)
+	if err != nil {
+		return 0, err
+	}
+
+	switch {
+	case n == 0:
+		return 0, nil
+	case n <= lenSize:
+		return 0, ErrInvalidPktLen
+	case n > OversizePayloadMax+lenSize:
+		return 0, ErrInvalidPktLen
+	default:
+		return n - lenSize, nil
+	}
+}
+
+// Turns the hexadecimal representation of a number in a byte slice into
+// a number. This function substitute strconv.ParseUint(string(buf), 16,
+// 16) and/or hex.Decode, to avoid generating new strings, thus helping the
+// GC.
+func hexDecode(buf [lenSize]byte) (int, error) {
+	var ret int
+	for i := 0; i < lenSize; i++ {
+		n, err := asciiHexToByte(buf[i])
+		if err != nil {
+			return 0, ErrInvalidPktLen
+		}
+		ret = 16*ret + int(n)
+	}
+	return ret, nil
+}
+
+// turns the hexadecimal ascii representation of a byte into its
+// numerical value.  Example: from 'b' to 11 (0xb).
+func asciiHexToByte(b byte) (byte, error) {
+	switch {
+	case b >= '0' && b <= '9':
+		return b - '0', nil
+	case b >= 'a' && b <= 'f':
+		return b - 'a' + 10, nil
+	default:
+		return 0, ErrInvalidPktLen
+	}
+}