stop saving of docker build cache when run by PRs from forks and build x86 and arm64 image in parallel

.github/workflows/build-push-backend.yml

@@ -36,7 +36,6 @@ jobs:
   lint-backend:
     name: Lint Python Code
     runs-on: ubuntu-latest
-
     steps:
       - uses: actions/checkout@v4
       - uses: astral-sh/ruff-action@v3
@@ -61,10 +60,15 @@ jobs:
         run: npm run lint
         working-directory: ./web
 
-
-  build-and-push:
+  build:
     needs: [lint-frontend, lint-backend]
     runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        platform:
+          - linux/amd64
+          - linux/arm64
     permissions:
       contents: read
       packages: write
@@ -77,6 +81,10 @@ jobs:
         id: repo_name
         run: echo "name=$(echo '${{ github.event.repository.name }}' | tr '[:upper:]' '[:lower:]')" >> $GITHUB_OUTPUT
 
+      - name: Prepare platform slug
+        id: platform_slug
+        run: echo "slug=${{ matrix.platform }}" | tr '/' '-' >> $GITHUB_OUTPUT
+
       - name: Set up QEMU
         uses: docker/setup-qemu-action@v3
 
@@ -104,7 +112,85 @@ jobs:
           fi
           echo "version=$VERSION" >> $GITHUB_OUTPUT
 
-      - name: Extract metadata (tags, labels) for Docker
+      - name: Extract metadata (labels only)
+        id: meta
+        uses: docker/metadata-action@v5
+        with:
+          images: ghcr.io/${{ github.repository_owner }}/${{ steps.repo_name.outputs.name }}/mediamanager
+
+      - name: Build and push by digest
+        id: build
+        uses: docker/build-push-action@v6
+        with:
+          context: .
+          file: ./Dockerfile
+          platforms: ${{ matrix.platform }}
+          labels: ${{ steps.meta.outputs.labels }}
+          outputs: type=image,name=ghcr.io/${{ github.repository_owner }}/${{ steps.repo_name.outputs.name }}/mediamanager,push-by-digest=true,name-canonical=true,push=${{ github.event_name != 'pull_request' || github.event.pull_request.head.repo.full_name == github.repository }}
+          build-args: |
+            VERSION=${{ steps.version.outputs.version }}
+            BASE_PATH=
+          cache-from: type=registry,ref=ghcr.io/${{ github.repository_owner }}/${{ steps.repo_name.outputs.name }}/mediamanager:buildcache-${{ steps.platform_slug.outputs.slug }}
+          cache-to: ${{ (github.event_name != 'pull_request' || github.event.pull_request.head.repo.full_name == github.repository) && format('type=registry,ref=ghcr.io/{0}/{1}/mediamanager:buildcache-{2},mode=max', github.repository_owner, steps.repo_name.outputs.name, steps.platform_slug.outputs.slug) || '' }}
+          no-cache: ${{ github.event_name == 'pull_request' && github.event.pull_request.head.repo.full_name != github.repository }}
+
+      - name: Export digest
+        run: |
+          mkdir -p /tmp/digests
+          digest="${{ steps.build.outputs.digest }}"
+          touch "/tmp/digests/${digest#sha256:}"
+
+      - name: Upload digest
+        uses: actions/upload-artifact@v4
+        with:
+          name: digests-backend-${{ strategy.job-index }}
+          path: /tmp/digests/*
+          if-no-files-found: error
+          retention-days: 1
+
+  merge:
+    needs: build
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      packages: write
+    if: github.event_name != 'pull_request' || github.event.pull_request.head.repo.full_name == github.repository
+    steps:
+      - name: Download digests
+        uses: actions/download-artifact@v4
+        with:
+          pattern: digests-backend-*
+          path: /tmp/digests
+          merge-multiple: true
+
+      - name: Set repository name to lowercase
+        id: repo_name
+        run: echo "name=$(echo '${{ github.event.repository.name }}' | tr '[:upper:]' '[:lower:]')" >> $GITHUB_OUTPUT
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Log in to GitHub Container Registry
+        uses: docker/login-action@v3
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Extract version
+        id: version
+        run: |
+          if [[ "${{ github.event_name }}" == "release" ]]; then
+            VERSION="${{ github.event.release.tag_name }}"
+          elif [[ "${{ github.ref_type }}" == "tag" ]]; then
+            VERSION="${{ github.ref_name }}"
+          else
+            DATE_STAMP=$(date -u +'%Y.%m.%d')
+            VERSION="dev-${DATE_STAMP}-${{ github.run_number }}"
+          fi
+          echo "version=$VERSION" >> $GITHUB_OUTPUT
+
+      - name: Extract metadata (tags)
         id: meta
         uses: docker/metadata-action@v5
         with:
@@ -119,18 +205,12 @@ jobs:
             type=semver,pattern={{major}}
             type=sha
 
-      - name: Build and push Docker image
-        uses: docker/build-push-action@v6
-        with:
-          context: .
-          file: ./Dockerfile
-          platforms: linux/amd64,linux/arm64
-          push: ${{ github.event_name != 'pull_request' || github.event.pull_request.head.repo.full_name == github.repository }}
-          tags: ${{ steps.meta.outputs.tags }}
-          labels: ${{ steps.meta.outputs.labels }}
-          build-args: |
-            VERSION=${{ steps.version.outputs.version }}
-            BASE_PATH=
-          cache-from: type=registry,ref=ghcr.io/${{ github.repository_owner }}/${{ steps.repo_name.outputs.name }}/mediamanager:buildcache
-          cache-to: type=registry,ref=ghcr.io/${{ github.repository_owner }}/${{ steps.repo_name.outputs.name }}/mediamanager:buildcache,mode=max
-          no-cache: ${{ github.event_name == 'pull_request' && github.event.pull_request.head.repo.full_name != github.repository }}
+      - name: Create manifest list and push
+        working-directory: /tmp/digests
+        run: |
+          docker buildx imagetools create $(jq -cr '.tags | map("-t " + .) | join(" ")' <<< "$DOCKER_METADATA_OUTPUT_JSON") \
+            $(printf 'ghcr.io/${{ github.repository_owner }}/${{ steps.repo_name.outputs.name }}/mediamanager@sha256:%s ' *)
+
+      - name: Inspect image
+        run: |
+          docker buildx imagetools inspect ghcr.io/${{ github.repository_owner }}/${{ steps.repo_name.outputs.name }}/mediamanager:${{ steps.version.outputs.version }}