ci: add script and config to mirror images to local CI registry

This script reads images.txt and copies the images from docker.io (or
other registries) to the local registry in the CI.

Signed-off-by: Niels de Vos <ndevos@redhat.com>

mirror/images.txt

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+# images.txt
+#
+# These lists contain the images that need to get mirrored from public
+# registries to the local CI registry.
+#
+# format: <full-image-spec> <short-name>
+#
+
+# ceph-csi v3.4
+docker.io/ceph/ceph:v16		ceph/ceph:v16
+docker.io/rook/ceph:v1.6.2	rook/ceph:v1.6.2
+
+# ceph-csi v3.3
+docker.io/ceph/ceph:v15		ceph/ceph:v15
+docker.io/rook/ceph:v1.4.9	rook/ceph:v1.4.9
+
+# e2e testing
+docker.io/library/busybox:1.29	library/busybox:1.29
+docker.io/library/nginx:latest	library/nginx:latest
+docker.io/library/vault:latest	library/vault:latest

mirror/mirror-images.sh

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+#!/bin/bash
+#
+# Mirror images listed in images.txt to the internal CI registry.
+#
+# Set DOCKER_CONFIG_JSON to the contents of ~/.docker/config.json to use the
+# authentication details from a cached configuration file.
+#
+# Set CI_REGISTRY_USER and CI_REGISTRY_PASSWD with the login details for the CI
+# registry.
+#
+
+CI_REGISTRY='registry-ceph-csi.apps.ocp.ci.centos.org'
+
+# get_image_entries returns the contents of images.txt without comments or empty lines
+function get_image_entries() {
+	grep -v -e '^#' -e '^$' images.txt
+}
+
+# create a temporary containers/auth.json for skopeo usage
+REGISTRY_AUTH_FILE="$(mktemp -t)"
+export REGISTRY_AUTH_FILE
+
+# make the temporary containers/auth.json a valid json file
+echo '{}' > "${REGISTRY_AUTH_FILE}"
+
+# if DOCKER_CONFIG_JSON is non-empty, use the credentials from there
+if [ -n "${DOCKER_CONFIG_JSON}" ]
+then
+	echo 'using ~/docker/config.json from env:DOCKER_CONFIG_JSON'
+	echo "${DOCKER_CONFIG_JSON}" > "${REGISTRY_AUTH_FILE}"
+fi
+
+# login on the CI registry if the user/passwd are available
+if [ -n "${CI_REGISTRY_USER}" ] && [ -n "${CI_REGISTRY_PASSWD}" ]
+then
+	echo 'using CI registry login from env:CI_REGISTRY_USER and env:CI_REGISTRY_PASSWD'
+	skopeo login \
+		--username="${CI_REGISTRY_USER}" \
+		--password="${CI_REGISTRY_PASSWD}" \
+		"${CI_REGISTRY}"
+fi
+
+# read each line from get_image_entries() into an array
+while read -r -a IMAGE_ENTRY
+do
+	# 1st entry in the array is the source
+	# 2nd entry in the array is the destination in the CI registry
+	SRC="docker://${IMAGE_ENTRY[0]}"
+	DST="docker://${CI_REGISTRY}/${IMAGE_ENTRY[1]}"
+	echo "going to copy ${SRC} to ${DST}" 
+	skopeo copy "${SRC}" "${DST}"
+done <<< "$(get_image_entries)"