cpiocat: add AppendDir

cpiocat/cpiocat.go

@@ -157,6 +157,24 @@ func (c *Cat) AppendFile(srcPath, archPath string) (r *Cat) {
 	return
 }
 
+func (c *Cat) AppendDir(archPath string, mode cpio.FileMode) (r *Cat) {
+	r = c
+	if c.err != nil {
+		return
+	}
+
+	var err error
+	defer func() { c.err = err }()
+
+	const DIR_FLAG = 0o004 << 12
+	err = c.cout.WriteHeader(&cpio.Header{
+		Name: archPath,
+		Mode: mode | DIR_FLAG,
+	})
+
+	return
+}
+
 func (c *Cat) AppendBytes(content []byte, archPath string, mode cpio.FileMode) (r *Cat) {
 	r = c
 	if c.err != nil {