turnstone/.github/workflows/docker-publish.yml

name: Publish Docker Image

on:
  workflow_run:
    workflows: ["CI"]
    types: [completed]

concurrency:
  group: docker-${{ github.event.workflow_run.head_sha }}
  # Never cancel mid-push: an interrupted multi-tag push can leave the
  # registry with a partial tag set (e.g. :latest moved, :stable not).
  cancel-in-progress: false

permissions:
  contents: read
  packages: write

env:
  REGISTRY: ghcr.io
  IMAGE_NAME: ${{ github.repository }}

jobs:
  docker:
    # Same gate as publish.yml: workflow_run fires for every CI completion
    # (including fork and same-repo PR runs) with this repo's token and
    # packages:write.  Only same-repo tag pushes may publish images; CI's
    # push trigger matches main/stable/* and v* tags, so a head_branch
    # starting with "v" is necessarily a tag run.
    if: >-
      github.event.workflow_run.conclusion == 'success' &&
      github.event.workflow_run.event == 'push' &&
      github.event.workflow_run.head_repository.full_name == github.repository &&
      startsWith(github.event.workflow_run.head_branch, 'v')
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7
        with:
          ref: ${{ github.event.workflow_run.head_sha }}
          fetch-depth: 0
          # The docker build only reads the tree; keep the token out of it.
          persist-credentials: false

      - name: Resolve release tag
        id: tag
        run: |
          TAG=$(git tag --points-at HEAD | grep '^v' | head -1)
          if [ -z "$TAG" ]; then
            echo "No v* tag at HEAD — skipping publish"
            echo "skip=true" >> "$GITHUB_OUTPUT"
          else
            echo "tag=${TAG}" >> "$GITHUB_OUTPUT"
            echo "skip=false" >> "$GITHUB_OUTPUT"
          fi

      - name: Log in to GHCR
        if: steps.tag.outputs.skip == 'false'
        uses: docker/login-action@af1e73f918a031802d376d3c8bbc3fe56130a9b0 # v4
        with:
          registry: ${{ env.REGISTRY }}
          username: ${{ github.actor }}
          password: ${{ secrets.GITHUB_TOKEN }}

      - name: Compute Docker tags
        if: steps.tag.outputs.skip == 'false'
        id: tags
        env:
          REF: ${{ steps.tag.outputs.tag }}
        run: |
          VERSION="${REF#v}"
          FULL="${REGISTRY}/${IMAGE_NAME}"
          FULL="${FULL,,}"

          if echo "$VERSION" | grep -qE '(a|b|rc)[0-9]+$'; then
            TAGS="${FULL}:${VERSION},${FULL}:experimental"
          else
            MINOR="${VERSION%.*}"
            TAGS="${FULL}:${VERSION},${FULL}:${MINOR},${FULL}:stable,${FULL}:latest"
          fi
          echo "tags=${TAGS}" >> "$GITHUB_OUTPUT"

      - uses: docker/setup-buildx-action@bb05f3f5519dd87d3ba754cc423b652a5edd6d2c # v4
        if: steps.tag.outputs.skip == 'false'

      - name: Build and push
        if: steps.tag.outputs.skip == 'false'
        uses: docker/build-push-action@53b7df96c91f9c12dcc8a07bcb9ccacbed38856a # v7
        with:
          context: .
          push: true
          tags: ${{ steps.tags.outputs.tags }}
          cache-from: type=gha
          cache-to: type=gha,mode=max