publish-on-release.yaml

# loosley based on https://docs.github.com/en/actions/publishing-packages/publishing-docker-images#publishing-images-to-github-packages
#
# a push to "/refs/heads/releases/v1" results in a tag of "releases-v1" per https://github.com/docker/metadata-action#usage

name: Create and publish a Docker image on release

on:
  push:
    branches: ['release']
  workflow_dispatch:

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

jobs:
  build-and-push-image-to-ghcr:
    runs-on: ubuntu-latest
    permissions:
      contents: read
      packages: write

    steps:
      - name: Checkout repo
        uses: actions/checkout@v3

      - name: Login to ghcr.io Container registry
        # should this be pinned?
        # https://github.com/docker/login-action
        uses: docker/login-action@v2.1.0
        with:
          registry: ${{ env.REGISTRY }}
          username: ${{ github.actor }}
          password: ${{ secrets.GHCR_TOKEN }}

      - name: Extract metadata (tags + labels) for Docker
        id: meta
        # should this be pinned?
        # https://github.com/docker/metadata-action
        uses: docker/metadata-action@v4.4.0
        with:
          images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}

      - name: Build and push Docker image
        # should this be pinned?
        # https://github.com/docker/build-push-action
        uses: docker/build-push-action@v4.0.0
        with:
          context: .
          push: true
          tags: ${{ steps.meta.outputs.tags }}
          labels: ${{ steps.meta.output.labels }}