docker-image.yml

name: Docker Image CI

on:
  push:
    branches:
      - "main"
      - "staging"
  pull_request:
    branches: ["main"]

env:
  REGISTRY: ghcr.io
  # github.repository as <account>/<repo>
  IMAGE_NAME: ${{ github.repository }}

jobs:
  build:
    runs-on: ubuntu-latest
    permissions:
      contents: read
      packages: write # might need to use PAT instead
      id-token: write

    steps:
      - name: Checkout repository
        uses: actions/checkout@v4

      # Install the cosign tool except on PR
      # https://github.com/sigstore/cosign-installer
      - name: Install cosign
        if: github.event_name != 'pull_request'
        uses: sigstore/cosign-installer@6e04d228eb30da1757ee4e1dd75a0ec73a653e06 #v3.1.1
        with:
          cosign-release: "v2.1.1"

      # Set up BuildKit Docker container builder to be able to build
      # multi-platform images and export cache
      # https://github.com/docker/setup-buildx-action
      - name: Set up Docker Buildx
        uses: docker/setup-buildx-action@f95db51fddba0c2d1ec667646a06c2ce06100226 # v3.0.0

      # Login against a Docker registry except on PR
      # https://github.com/docker/login-action
      - name: Log into registry ghcr.io
        if: github.event_name != 'pull_request'
        uses: docker/login-action@343f7c4344506bcbf9b4de18042ae17996df046d # v3.0.0
        with:
          registry: ${{ env.REGISTRY }}
          username: ${{ github.actor }}
          password: ${{ secrets.GITHUB_TOKEN }} # might need to use PAT instead

      # Extract metadata (tags, labels) for Docker
      # https://github.com/docker/metadata-action
      - name: Extract Docker metadata
        id: meta
        uses: docker/metadata-action@96383f45573cb7f253c731d3b3ab81c87ef81934 # v5.0.0
        with:
          tags: |
            type=raw,value=latest,enable={{is_default_branch}}
            type=ref,event=branch
            type=raw,value={{branch}}-{{date 'X'}},enable=${{ github.event_name != 'pull_request' }}
            type=raw,value={{base_ref}}-{{date 'X'}},enable=${{ github.event_name == 'pull_request' }}
          images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}

      # Build and push Docker image with Buildx (don't push on PR)
      # https://github.com/docker/build-push-action
      - name: Build and push Docker image
        id: build-and-push
        uses: docker/build-push-action@0565240e2d4ab88bba5387d719585280857ece09 # v5.0.0
        with:
          context: .
          push: ${{ github.event_name != 'pull_request' }}
          tags: ${{ steps.meta.outputs.tags }}
          labels: ${{ steps.meta.outputs.labels }}
          cache-from: type=gha
          cache-to: type=gha,mode=max

      # Sign the resulting Docker image digest except on PRs.
      # This will only write to the public Rekor transparency log when the Docker
      # repository is public to avoid leaking data.  If you would like to publish
      # transparency data even for private images, pass --force to cosign below.
      # https://github.com/sigstore/cosign
      - name: Sign the published Docker image
        if: ${{ github.event_name != 'pull_request' }}
        env:
          # https://docs.github.com/en/actions/security-guides/security-hardening-for-github-actions#using-an-intermediate-environment-variable
          TAGS: ${{ steps.meta.outputs.tags }}
          DIGEST: ${{ steps.build-and-push.outputs.digest }}
        # This step uses the identity token to provision an ephemeral certificate
        # against the sigstore community Fulcio instance.
        run: echo "${TAGS}" | xargs -I {} cosign sign --yes {}@${DIGEST}