Build multi-platform images that build on each other

[nwalters512]

Description

Scenario

I'm trying to use this action to build, for multiple platforms, a pair of images, e.g. foo-base and foo-specialized. foo-specialized uses foo-base as a base image, e.g.:

FROM foo-base:latest
# ...

I'd like to perform builds on both PRs and on my main branch:

• On PRs, I'll push a tag based on the Git SHA
• On the main branch, I'll push both the latest tag and a tag based on the Git SHA

Attempt

My initial attempt was just this:

      - name: Build and push foo-base
        uses: docker/build-push-action@v6
        with:
          context: path/to/base
          platforms: linux/amd64,linux/arm64
          push: true
          no-cache: true
          tags: foo-base:${{ github.event.pull_request.head.sha || github.sha }}

      - name: Build and push foo-specialized
        uses: docker/build-push-action@v6
        with:
          context: path/to/specialized
          platforms: linux/amd64,linux/arm64
          push: true
          no-cache: true
          tags: foo-specialized:${{ github.event.pull_request.head.sha || github.sha }}

However, this didn't work as there wasn't a latest tag for foo-base. So I tried changing things to load the image back into Docker and tag it as latest (I can't specify ...:latest in tags: because I don't want the latest tag pushed to Docker Hub for PR branches):

      - name: Build and push foo-base
        uses: docker/build-push-action@v6
        with:
          context: path/to/base
          platforms: linux/amd64,linux/arm64
          push: true
          load: true
          no-cache: true
          tags: foo-base:${{ github.event.pull_request.head.sha || github.sha }}

      - name: Tag foo-base as latest
        run: docker tag foo-base:${{ github.event.pull_request.head.sha || github.sha }} foo-base:latest

      - name: Build and push foo-specialized
        uses: docker/build-push-action@v6
        with:
          context: path/to/specialized
          platforms: linux/amd64,linux/arm64
          push: true
          no-cache: true
          tags: foo-specialized:${{ github.event.pull_request.head.sha || github.sha }}

However, that fails because of docker/buildx#59. The recommended solution for that was to use the containerd image store, but I don't see any documentation in this action about how to set that up or use it for image loading/exporting.

Question

Can you recommend any way to achieve what I want? It seems like using the containerd image store would be the way to go, but as I mentioned above, there's no documentation on this action about how to use it. Do you have any advice? Let me know if this is better suited to be a discussion, or if I should turn this into a concrete feature request, e.g. "let me configure this action to use containerd as the image store".