Docker workflow (nolar/kopf)

# Build and publish Kopf Docker images to ghcr.io.
# On PRs: build only (no push). On release tags: build and push with full tag matrix.
name: Docker
on:
  pull_request:  # only builds, no pushes (see the if condition on push:…)
    branches:
      - main
  release:
    types:
      - published
#  push:
#    tags:
#      - "[0-9]+.[0-9]+*"
  workflow_dispatch: {}
 
env:
  REGISTRY: ghcr.io
  IMAGE_NAME: ${{ github.repository }}
  DEFAULT_PYTHON: "3.14"
  DEFAULT_VARIANT: slim
 
concurrency:
  group: ${{ github.workflow }}-${{ github.ref }}
  cancel-in-progress: true
 
jobs:
  docker:
    timeout-minutes: 30
    strategy:
      fail-fast: false
      matrix:
        python-version: ["3.14"]  # all versions starting with 3.14 as the first one
        variant: [slim, alpine]
    name: Python ${{ matrix.python-version }} ${{ matrix.variant }}
    runs-on: latchkey-small
    permissions:
      contents: read
      packages: write
    steps:
      - uses: actions/checkout@v6
        with:
          fetch-depth: 0
 
      - uses: docker/setup-qemu-action@v4
      - uses: docker/setup-buildx-action@v4
 
      - uses: docker/login-action@v4
        with:
          registry: ${{ env.REGISTRY }}
          username: ${{ github.actor }}
          password: ${{ secrets.GITHUB_TOKEN }}
 
      - name: Compute version
        id: version
        run: |
          pip install setuptools-scm
          VERSION=$(python -m setuptools_scm)
          MAJOR=$(echo "$VERSION" | cut -d. -f1)
          MINOR=$(echo "$VERSION" | cut -d. -f1-2)
          PATCH=$(echo "$VERSION" | cut -d. -f1-3 | cut -d+ -f1 | cut -da -f1 | cut -db -f1 | cut -dr -f1 | cut -dd -f1)
          echo "version=$VERSION" >> "$GITHUB_OUTPUT"
          echo "major=$MAJOR" >> "$GITHUB_OUTPUT"
          echo "minor=$MINOR" >> "$GITHUB_OUTPUT"
          echo "patch=$PATCH" >> "$GITHUB_OUTPUT"
 
      - name: Compute tags
        id: tags
        run: |
          IMAGE="${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}"
          IMAGE=$(echo "$IMAGE" | tr '[:upper:]' '[:lower:]')
          PYTHON="${{ matrix.python-version }}"
          VARIANT="${{ matrix.variant }}"
          MAJOR="${{ steps.version.outputs.major }}"
          MINOR="${{ steps.version.outputs.minor }}"
          PATCH="${{ steps.version.outputs.patch }}"
          IS_DEFAULT_PYTHON=${{ matrix.python-version == env.DEFAULT_PYTHON }}
          IS_DEFAULT_VARIANT=${{ matrix.variant == env.DEFAULT_VARIANT }}
 
          TAGS=""
 
          if [ "${{ github.event_name }}" = "pull_request" ]; then
            PR="${{ github.event.pull_request.number }}"
            TAGS="${IMAGE}:pr-${PR}-python${PYTHON}-${VARIANT}"
          else
            # Always: full version + python + variant
            TAGS="${TAGS}${IMAGE}:${PATCH}-python${PYTHON}-${VARIANT}"
            TAGS="${TAGS},${IMAGE}:${MINOR}-python${PYTHON}-${VARIANT}"
            TAGS="${TAGS},${IMAGE}:v${MAJOR}-python${PYTHON}-${VARIANT}"
 
            # Default variant: version + python (no variant suffix)
            if [ "$IS_DEFAULT_VARIANT" = "true" ]; then
              TAGS="${TAGS},${IMAGE}:${PATCH}-python${PYTHON}"
              TAGS="${TAGS},${IMAGE}:${MINOR}-python${PYTHON}"
              TAGS="${TAGS},${IMAGE}:v${MAJOR}-python${PYTHON}"
            fi
 
            # Default python + default variant: bare version tags + latest
            if [ "$IS_DEFAULT_PYTHON" = "true" ] && [ "$IS_DEFAULT_VARIANT" = "true" ]; then
              TAGS="${TAGS},${IMAGE}:${PATCH}"
              TAGS="${TAGS},${IMAGE}:${MINOR}"
              TAGS="${TAGS},${IMAGE}:v${MAJOR}"
              TAGS="${TAGS},${IMAGE}:latest"
            fi
          fi
 
          echo "tags=$TAGS" >> "$GITHUB_OUTPUT"
 
      - uses: docker/build-push-action@v7
        with:
          context: .
          platforms: linux/amd64,linux/arm64
          file: docker/Dockerfile
          push: ${{ github.event_name != 'pull_request' }}
          tags: ${{ steps.tags.outputs.tags }}
          build-args: |
            PYTHON_VERSION=${{ matrix.python-version }}
            VARIANT=${{ matrix.variant }}