fix: derive buildah cache from snapshot image

  extends: .docker-base

  stage: package-build

  image: "$DOCKER_BUILDAH_IMAGE"

  variables:

    BUILDAH_BUILD_CACHE: "$CI_REGISTRY_IMAGE/snapshot/cache"

  script:

    - configure_containers_registries

    # derive buildah_build_cache repository

    - buildah_build_cache="${DOCKER_SNAPSHOT_IMAGE%:*}/cache"

    - log_info "Using ${buildah_build_cache} as build cache repository"

    # build and push image

    - buildah build --file "$DOCKER_FILE" --tag $DOCKER_SNAPSHOT_IMAGE --layers --cache-from $BUILDAH_BUILD_CACHE --cache-to $BUILDAH_BUILD_CACHE --build-arg http_proxy="$http_proxy" --build-arg https_proxy="$https_proxy" --build-arg no_proxy="$no_proxy" $DOCKER_METADATA $DOCKER_BUILD_ARGS "$(docker_context_path)"

    - buildah build --file "$DOCKER_FILE" --tag $DOCKER_SNAPSHOT_IMAGE --layers --cache-from $buildah_build_cache --cache-to $buildah_build_cache --build-arg http_proxy="$http_proxy" --build-arg https_proxy="$https_proxy" --build-arg no_proxy="$no_proxy" $DOCKER_METADATA $DOCKER_BUILD_ARGS "$(docker_context_path)"

    - buildah push --digestfile .img-digest.txt "$DOCKER_SNAPSHOT_IMAGE"

    # display digest of the resulting image

    - cat .img-digest.txt