Make cache keys unique

.github/workflows/flaskr-ci.yaml

@@ -35,14 +35,13 @@ jobs:
       # Required permission to push images with the built-in GITHUB_TOKEN
       packages: write
     runs-on: ubuntu-latest
-    env:
-      CACHE_KEY: flaskr-buildx-${{ github.ref_name }}
     steps:
       - uses: actions/checkout@v3
-      - name: Job vars and prep
+      - name: Job vars
         # Use bash string manipulation to create vars
         # Note runner context isn't available in job.env, so use it here
         # https://docs.github.com/en/actions/reference/context-and-expression-syntax-for-github-actions#context-availability
+        shell: bash
         run: |
           echo "SHA_SHORT=${GITHUB_SHA:0:10}" >> ${GITHUB_ENV}
           echo "REPO_LOWER_CASE=${GITHUB_REPOSITORY,,}" >> ${GITHUB_ENV}
@@ -56,9 +55,9 @@ jobs:
         uses: actions/cache@v2
         with:
           path: ${{ env.CACHE_DIR }}
-          key: ${{ env.CACHE_KEY }}
+          key: buildx-flaskr-${{ github.sha }}
           restore-keys: |
-            flaskr-buildx-main
+            buildx-flaskr-
       - name: Login to GitHub Container Registry
         uses: docker/login-action@v2
         with:
@@ -73,16 +72,12 @@ jobs:
           tags: "ghcr.io/${{ env.REPO_LOWER_CASE }}:${{ env.SHA_SHORT }}"
           cache-from: type=local,src=${{ env.CACHE_DIR }}
           cache-to: type=local,dest=${{ env.NEW_CACHE_DIR }}
-      # Only save the latest Docker build layers to the cache, otherwise
-      # the cache will keep growing indefinitely, past the 10GB max
+      # Only save the latest Docker build layers to new cache key, otherwise
+      # new cache keys will keep getting bigger indefinitely
       # https://github.com/docker/build-push-action/issues/252
       # https://github.com/moby/buildkit/issues/1896
-      # - name: Only persist the new cache layers
-      #   run: |
-      #     rm -rf ${CACHE_DIR}
-      #     mv ${NEW_CACHE_DIR} ${CACHE_DIR}
+      # Thanks https://evilmartians.com/chronicles/build-images-on-github-actions-with-docker-layer-caching
       - name: Only persist the new cache layers
-        uses: actions/cache/save@v3
-        with:
-          path: ${{ env.NEW_CACHE_DIR }}
-          key: ${{ env.CACHE_KEY }}
+        run: |
+          rm -rf ${CACHE_DIR}
+          mv ${NEW_CACHE_DIR} ${CACHE_DIR}