Add multi-architecture (amd64/arm64) container builds with GHCR support

.github/workflows/build-push.yml

@@ -0,0 +1,51 @@
+name: Build and Push Multi-arch Image
+
+on:
+  push:
+    branches:
+      - php*
+  workflow_dispatch:
+
+jobs:
+  build-push:
+    name: Build and push multi-arch image
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      packages: write
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Extract base image tag from Dockerfile
+        id: extract-tag
+        run: |
+          # Extract FROM line and convert php:8.3-apache → php8.3-apache
+          BASE_IMAGE=$(grep -m1 '^FROM' Dockerfile | awk '{print $2}')
+          TAG=$(echo "$BASE_IMAGE" | tr ':' '-' | tr '/' '-')
+          echo "tag=$TAG" >> $GITHUB_OUTPUT
+          echo "Extracted tag: $TAG"
+
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v3
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Login to GHCR
+        uses: docker/login-action@v3
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Build and push
+        uses: docker/build-push-action@v6
+        with:
+          context: .
+          platforms: linux/amd64,linux/arm64
+          push: true
+          tags: ghcr.io/${{ github.repository }}:${{ steps.extract-tag.outputs.tag }}
+          cache-from: type=gha
+          cache-to: type=gha,mode=max

README.md

@@ -19,9 +19,23 @@ docker-compose stop
 
 ## Building the Docker image
 
-The Docker image lives in [Docker Hub](https://hub.docker.com/repository/docker/localgovdrupal/apache-php). Ask in [Slack](https://localgovdrupal.slack.com/) if you need the permissions to push new images.
+### Automated builds (GHCR)
 
-Build with:
+Multi-architecture images (amd64/arm64) are automatically built and pushed to GitHub Container Registry on every push to `php*` branches:
+
+```
+ghcr.io/<owner>/drupal-container:<php-version>-apache
+```
+
+For example: `ghcr.io/localgovdrupal/drupal-container:php-8.3-apache`
+
+You can also trigger a build manually via the [Actions tab](../../actions/workflows/build-push.yml).
+
+### Manual builds (Docker Hub)
+
+The Docker image also lives in [Docker Hub](https://hub.docker.com/repository/docker/localgovdrupal/apache-php). Ask in [Slack](https://localgovdrupal.slack.com/) if you need the permissions to push new images.
+
+Build and push manually with:
 
 ```bash
 export branch=$(git symbolic-ref --short HEAD)