Make compatible with Docker Metadata action

[aaronadamsCA]

It would be really nice if this action were compatible with the Docker Metadata action, so that tags could be generated by that action and easily passed to this action.

Right now, if you do this:

      - id: metadata
        uses: docker/metadata-action@v4
        with:
          tags: |
            type=ref,event=branch
            type=ref,event=pr
            type=semver,pattern={{version}}
      - uses: devcontainers/[email protected]
        with:
          imageTag: "${{ join(steps.metadata.outputs.tags) }}"

The result is a Docker error, because steps.metadata.outputs.tags is already in the format "{image}:{tag}"[], and this action prepends each tag with {image}: again. Docker doesn't like -t {image}:{image}:{tag} and errors out.

If this action could check each tag to see if it's already prepended with the image name before doing so, then I think it would be directly compatible with the official Docker action.

[nickzelei]

Would love to see this as I just hit the same issue.

I was able to work around it by adding an intermediary step to get the tags in the format necessary.

I have the metadata outputting the tags with a , separator, but it should work in the default, multi-line format. Just update the delimiter in the script to be \n instead of ,.

The script looks like this:

prefix="ghcr.io/${{ github.repository }}/devcontainer"
input_list="$DOCKER_METADATA_OUTPUT_TAGS"
delimiter=","

result_list=$(echo "$input_list" | sed "s|${prefix}:||g")

echo "tags=$result_list" >> "$GITHUB_OUTPUT"

The workflow as such:

steps:
  - name: Checkout
    id: checkout
    uses: actions/checkout@v4

  - name: Docker meta
    id: meta
    uses: docker/metadata-action@v5
    with:
      # list of Docker images to use as base name for tags
      images: |
        name=ghcr.io/${{ github.repository }}/devcontainer
      # generate Docker tags based on the following events/attributes
      tags: |
        type=match,pattern=devcontainer/v(\d.\d.\d),group=1
      sep-tags: ","

  - name: Update Tags to Fit into devcontainers/cli format
    id: dcmeta
    run: |
      prefix="ghcr.io/${{ github.repository }}/devcontainer"
      input_list="$DOCKER_METADATA_OUTPUT_TAGS"
      delimiter=","

      result_list=$(echo "$input_list" | sed "s|${prefix}:||g")

      echo "tags=$result_list" >> "$GITHUB_OUTPUT"

  - name: Set up QEMU
    uses: docker/setup-qemu-action@v3
    with:
      platforms: linux/amd64,linux/arm64

  - name: Set up Docker Buildx
    uses: docker/setup-buildx-action@v3

  - name: Login to GHCR
    uses: docker/login-action@v3
    with:
      registry: ghcr.io
      username: ${{ github.repository_owner }}
      password: ${{ secrets.GITHUB_TOKEN }}

  - name: Build and release devcontainer Multi-Platform
    uses: devcontainers/[email protected]
    env:
      # see: https://github.com/devcontainers/ci/issues/191#issuecomment-1603857155
      BUILDX_NO_DEFAULT_ATTESTATIONS: true
    with:
      imageName: ghcr.io/${{ github.repository }}/devcontainer
      imageTag: ${{ steps.dcmeta.outputs.tags }}
      cacheFrom: ghcr.io/${{ github.repository }}/devcontainer
      platform: linux/amd64,linux/arm64
      push: always