ci(docker): fix multiplatform build on multiple runners overriding

see docker/build-push-action#671

.github/workflows/docker-build.yml

@@ -15,8 +15,11 @@ on:
       - Dockerfile
       - .github/workflows/docker-build.yml
 
+env:
+  REGISTRY_IMAGE: ghcr.io/retrorealm/playmatch
+
 jobs:
-  docker:
+  build:
     strategy:
       matrix:
         platform: [ ubuntu-latest, linux-arm64 ]
@@ -30,7 +33,7 @@ jobs:
         id: meta
         uses: docker/metadata-action@v5
         with:
-          images: ghcr.io/retrorealm/playmatch
+          images: ${{ env.REGISTRY_IMAGE }}
           tags: |
             type=ref,event=branch
             type=ref,event=pr
@@ -50,18 +53,73 @@ jobs:
           username: ${{ github.actor }}
           password: ${{ secrets.GITHUB_TOKEN }}
 
-      - name: Build and push
-        id: docker_build
-        uses: docker/build-push-action@v5
+      - name: Build and push by digest
+        id: build
+        uses: docker/build-push-action@v6
         with:
           context: .
           file: Dockerfile
           push: ${{ github.event_name != 'pull_request' }}
           tags: ${{ steps.meta.outputs.tags }}
           labels: ${{ steps.meta.outputs.labels }}
           annotations: ${{ steps.meta.outputs.annotations }}
-          cache-from: type=gha
-          cache-to: type=gha,mode=max
+          outputs: type=image,name=${{ env.REGISTRY_IMAGE }},push-by-digest=true,name-canonical=true,push=true
+          cache-from: type=gha,scope=build-${{ matrix.platform }}
+          cache-to: type=gha,scope=build-${{ matrix.platform }}
+
+      - 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-${{ env.PLATFORM_PAIR }}
+          path: /tmp/digests/*
+          if-no-files-found: error
+          retention-days: 1
+
+  merge:
+    runs-on: ubuntu-latest
+    needs:
+      - build
+    steps:
+      - name: Download digests
+        uses: actions/download-artifact@v4
+        with:
+          path: /tmp/digests
+          pattern: digests-*
+          merge-multiple: true
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Docker metadata extraction
+        id: meta
+        uses: docker/metadata-action@v5
+        with:
+          images: ${{ env.REGISTRY_IMAGE }}
+          tags: |
+            type=ref,event=branch
+            type=ref,event=pr
+            type=ref,event=tag
+            type=sha
+
+      - name: Login to GitHub Container Registry
+        uses: docker/login-action@v3
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - 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") \
+            $(printf '${{ env.REGISTRY_IMAGE }}@sha256:%s ' *)
 
-      - name: Image digest
-        run: echo ${{ steps.docker_build.outputs.digest }}
+      - name: Inspect image
+        run: |
+          docker buildx imagetools inspect ${{ env.REGISTRY_IMAGE }}:${{ steps.meta.outputs.version }}