Cache Docker layers when (re)building a Docker image on GitHub Actions.

cache-docker-layers-on-github-actions.yml

# source: https://github.com/docker/buildx/pull/535#issuecomment-869022231

  e2e:
    name: End-to-end tests against Docker containers
    runs-on: ubuntu-latest
    env:
      DOCKER_BUILDKIT: '1' # to enable persistent docker cache
      COMPOSE_DOCKER_CLI_BUILD: '1' # so docker-compose commands benefits from buildkit/buildx's docker cache
    steps:
      - uses: actions/checkout@v2

      # Use GitHub's Docker registry to cache layers and reduce image build time from a run to the other
      - run: echo ${{ secrets.GITHUB_TOKEN }} | docker login docker.pkg.github.com -u $GITHUB_ACTOR --password-stdin
      - run: docker pull docker.pkg.github.com/$GITHUB_REPOSITORY/admin-api-cached-build || true
      - run: docker build . --file Dockerfile-local --tag admin-api --cache-from=docker.pkg.github.com/$GITHUB_REPOSITORY/admin-api-cached-build --build-arg BUILDKIT_INLINE_CACHE=1
      - run: docker tag admin-api docker.pkg.github.com/$GITHUB_REPOSITORY/admin-api-cached-build && docker push docker.pkg.github.com/$GITHUB_REPOSITORY/admin-api-cached-build || true
      # source: https://dev.to/dtinth/caching-docker-builds-in-github-actions-which-approach-is-the-fastest-a-research-18ei

      - name: 'Build admin-api with docker-compose' # so the test suite does not have to
        run: docker-compose -f docker-compose-local.yml build admin-api
      - name: Run end-to-end tests
        run: yarn test:e2e:docker # starts the APIs and services with docker-compose before running tests

      - name: "Push Docker images to cache"
        run: docker push --all-tags ghcr.io/$GITHUB_REPOSITORY/admin-api-cached-build || true