Initial version

.gitlab-ci.yml

+---
+variables:
+  IMAGE_NAMES: 'ubi ubi-minimal ubi-init'
+  REMOTE_REGISTRY: 'registry.access.redhat.com'
+
+stages:
+  - mirror
+
+mirror:
+  stage: mirror
+  image:
+    # Use the 'debug' image as it provides a shell which is needed for GitLab CI
+    name: gcr.io/go-containerregistry/crane:debug
+    entrypoint: [""]
+  variables:
+    # No need to clone the repo
+    GIT_STRATEGY: none
+  script:
+    - crane auth login -u "$CI_REGISTRY_USER" -p "$CI_REGISTRY_PASSWORD" "$CI_REGISTRY"
+    - |
+      for IMAGE in ${IMAGE_NAMES}; do
+        echo -e "\e[1m\e[32m Listing tags for: ${REMOTE_REGISTRY}/${CI_PROJECT_NAME}/${IMAGE} \e[0m"
+        TAGS=$(crane ls ${REMOTE_REGISTRY}/${CI_PROJECT_NAME}/${IMAGE})
+        NUM_TAGS=$(echo "${TAGS}" | wc -l)
+        echo -e "\e[32m  -> ${NUM_TAGS} tags found.\e[0m"
+
+        for TAG in $TAGS; do
+          SRC_DIGEST=$(crane manifest ${REMOTE_REGISTRY}/${CI_PROJECT_NAME}/${IMAGE}:${TAG} | grep digest)
+          set +e
+          DST_DIGEST=$(crane manifest ${CI_REGISTRY_IMAGE}/${IMAGE}:${TAG} 2>/dev/null | grep digest)
+          set -e
+
+          if [[ "$SRC_DIGEST" != "$DST_DIGEST" ]]; then
+            echo -e "\e[1m\e[32m Copying ${REMOTE_REGISTRY}/${CI_PROJECT_NAME}/${IMAGE}:${TAG} to ${CI_REGISTRY_IMAGE}/${IMAGE}:${TAG} \e[0m"
+            crane copy ${REMOTE_REGISTRY}/${CI_PROJECT_NAME}/${IMAGE}:${TAG} ${CI_REGISTRY_IMAGE}/${IMAGE}:${TAG}
+          fi
+        done
+
+        echo -e "\e[1m\e[32m Done with ${REMOTE_REGISTRY}/${CI_PROJECT_NAME}/${IMAGE} \e[0m"
+      done
\ No newline at end of file