images.yaml

name: Create and publish a Container image

on:
  push:
    branches:
      - master         # Trigger the workflow on push to the master branch
    tags:
      - 'v*'           # Trigger the workflow on tags like v1.0.0, v2.0.0, etc.
  pull_request:
    branches:
      - master         # Trigger workflow when a PR targets the master branch

permissions:
  contents: read
  packages: write
  id-token: write

# Defines two custom environment variables for the workflow. These are used for the Container registry domain, and a name for the Docker image that this workflow builds.
env:
  REGISTRY: ghcr.io
  IMAGE_NAME: ${{ github.repository }}

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

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

      # Logs in to the Container registry using GitHub token
      - name: Log in to the Container registry
        uses: docker/login-action@65b78e6e13532edd9afa3aa52ac7964289d1a9c1
        with:
          registry: ${{ env.REGISTRY }}
          username: ${{ github.actor }}
          password: ${{ secrets.GITHUB_TOKEN }}

      # Extract metadata (tags, labels) for Docker
      - name: Extract metadata (tags, labels) for Docker
        id: meta
        uses: docker/metadata-action@9ec57ed1fcdbf14dcef7dfbe97b2010124a938b7
        with:
          images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}

      # Build and push Docker image
      - name: Build and push Docker image
        uses: docker/build-push-action@f2a1d5e99d037542a71f64918e516c093c6f3fc4
        with:
          context: .
          push: true
          # Tags the image as 'latest' only for master branch, versioned tags for versioned pushes, and PR-specific tags
          tags: |
            # Version tags for releases
            ${{ steps.meta.outputs.tags }}
            
            # Latest tag for master branch only
            ${{ github.ref == 'refs/heads/master' && env.REGISTRY }}/${{ env.IMAGE_NAME }}:latest
            
            # PR-specific tag (only applies during PR events)
            ${{ github.event_name == 'pull_request' && env.REGISTRY }}/${{ env.IMAGE_NAME }}:pr-${{ github.event.pull_request.number }}
            
            # Commit SHA for PR builds for more precise versioning
            ${{ github.event_name == 'pull_request' && env.REGISTRY }}/${{ env.IMAGE_NAME }}:${{ github.sha }}
            
          labels: ${{ steps.meta.outputs.labels }}