gitlab-ci to create container image for usage in gitlab-ci

See: https://docs.gitlab.com/ee/ci/testing/code_quality.html#required-images
Signed-off-by: Matthias Blümel <blaimi@blaimi.de>

.gitlab-ci.yml

@@ -0,0 +1,42 @@
+image-build:
+  image:
+    name: quay.io/buildah/stable:latest
+  stage: build
+  before_script:
+    - 'echo "$CI_REGISTRY_PASSWORD" | buildah login --username "$CI_REGISTRY_USER" --password-stdin $CI_REGISTRY'
+  script:
+    # more than two levels are forbidden -> using `-cache` instead of `/cache`
+    # https://docs.gitlab.com/ee/user/packages/container_registry/#naming-convention-for-your-container-images
+    - buildah bud
+      -f "Containerfile"
+      -t "$CI_REGISTRY_IMAGE/codeclimate/codeclimate-openapi:latest"
+      --layers
+      --cache-from=$CI_REGISTRY_IMAGE/codeclimate/codeclimate-openapi-cache
+      --cache-to=$CI_REGISTRY_IMAGE/codeclimate/codeclimate-openapi-cache
+      .
+    - buildah push "$CI_REGISTRY_IMAGE/codeclimate/codeclimate-openapi:latest"
+
+copy-upstream:
+  stage: deploy
+  image:
+    name: quay.io/skopeo/stable:latest
+    entrypoint: [""]
+  before_script:
+    - 'echo "$CI_REGISTRY_PASSWORD" | skopeo login --username "$CI_REGISTRY_USER" --password-stdin $CI_REGISTRY'
+  script:
+    - 'skopeo copy "docker://docker.io/${image_name}" "docker://$CI_REGISTRY_IMAGE/${image_name}"'
+  parallel:
+    matrix:
+      - image_name:
+          - codeclimate/codeclimate:0.94.0
+          - codeclimate/codeclimate:0.96.0
+          - codeclimate/codeclimate:latest
+          - codeclimate/codeclimate-structure:latest
+          - codeclimate/codeclimate-csslint:latest
+          - codeclimate/codeclimate-coffeelint:latest
+          - codeclimate/codeclimate-duplication:latest
+          - codeclimate/codeclimate-eslint:latest
+          - codeclimate/codeclimate-fixme:latest
+          - codeclimate/codeclimate-rubocop:latest
+  rules:
+    - if: $CI_PIPELINE_SOURCE == "schedule"