docker-merge.yml

name: Merge images

on:
  workflow_dispatch:  # allow explicit dispatches from arch-specific builds
  workflow_call:    # allow this workflow to be called by another workflow

env:
  IMAGE: ${{ vars.DOCKERHUB_IMAGE }}
  REGISTRY: docker.io

concurrency:  # ensure only one merge runs at a time
  group: merge-manifest
  cancel-in-progress: false

jobs:
  merge:
    runs-on: ubuntu-latest
    steps:
      - name: Login to DockerHub
        uses: docker/login-action@v3
        with: # these are defined in the GitHub Secrets UI
          username: ${{ secrets.DOCKERHUB_USERNAME }}
          password: ${{ secrets.DOCKERHUB_TOKEN }}

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

      # Merge the multiple architecture-specific images into a single multi-arch image.
      # If images for other architectures do not exist in the registry yet, this step will fail.
      # It will only succeed when at least one image for each architecture has been built and pushed.
      # If images for other architectures are being built and the ones in the registry
      # are old, it only updates the nightly tag for the architecture that triggered this
      # workflow. When images for other architectures are built successfully later, they will
      # trigger this workflow again and merge the updated images.
      - name: Create multi-arch manifest
        run: |
          docker buildx imagetools create \
            -t ${REGISTRY}/${IMAGE}:nightly \
            ${REGISTRY}/${IMAGE}:nightly-linux-amd64 \
            ${REGISTRY}/${IMAGE}:nightly-linux-arm64

      - name: Verify multi-arch manifest
        run: |
          docker buildx imagetools inspect ${REGISTRY}/${IMAGE}:nightly