Docker image layer caching using GHA cache

.github/workflows/docker-publish.yml

@@ -15,6 +15,14 @@ jobs:
       -
         name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v1
+      -
+        name: Cache Docker layers
+        uses: actions/cache@v2
+        with:
+          path: /tmp/.buildx-cache
+          key: ${{ runner.os }}-buildx-${{ github.sha }}
+          restore-keys: |
+            ${{ runner.os }}-buildx-
       -
         name: Login to DockerHub
         uses: docker/login-action@v1
@@ -27,4 +35,13 @@ jobs:
         with:
           context: .
           push: true
-          tags: luth31/fosscord-api:latest
+          tags: luth31/fosscord-api:latest
+          cache-from: type=local,src=/tmp/.buildx-cache
+          cache-to: type=local,dest=/tmp/.buildx-cache-new
+      -
+        # Hackfix to cleanup cache; replace after buildx 0.6 and BuildKit 0.9 are released
+        # https://github.com/docker/build-push-action/pull/406#issuecomment-879184394
+        name: Move cache fix
+        run: |
+          rm -rf /tmp/.buildx-cache
+          mv /tmp/.buildx-cache-new /tmp/.buildx-cache