buildx cache

.github/workflows/build.yaml

@@ -49,11 +49,19 @@ jobs:
           username: ${{ secrets.DOCKER_USERNAME }}
           password: ${{ secrets.DOCKER_TOKEN }}
 
+      - name: Cache Docker layers
+        uses: actions/cache@v2
+        with:
+          path: /tmp/.buildx-cache
+          key: ${{ runner.os }}-buildx-dir
+
       - name: Build and push
         uses: docker/build-push-action@v2
         with:
           context: .
           file: Dockerfile
           platforms: linux/amd64, linux/arm64, linux/arm/v7
-          push: true
+          push: ${{ github.event_name != 'pull_request' }}
           tags: ${{ steps.prep.outputs.tags }}
+          cache-from: type=local,src=/tmp/.buildx-cache
+          cache-to: type=local,dest=/tmp/.buildx-cache