Add docker build to CI pipeline

.github/workflows/flaskr-ci.yaml

@@ -3,10 +3,8 @@ name: Build Flaskr App
 on: [push]
 
 jobs:
-  build:
-
+  tests:
     runs-on: ubuntu-latest
-
     steps:
       - uses: actions/checkout@v3
       - name: Set up Python 3.11
@@ -32,3 +30,49 @@ jobs:
           pwd
           cd examples/tutorial
           pytest
+  # Build Docker image in a separate job so that it's not taited by cached python build/test files
+  build-image:
+    needs: tests
+    permissions:
+      # Required permission to push images with the built-in GITHUB_TOKEN
+      packages: write
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - name: Set job vars
+        id: vars
+        run: echo "sha_short=${GITHUB_SHA:0:10}" >> $GITHUB_OUTPUT
+      # This is a separate action that sets up buildx runner
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v1
+      # So now you can use Actions' own caching!
+      - name: Cache Docker layers
+        uses: actions/cache@v2
+        with:
+          path: /tmp/.buildx-cache
+          key: flaskr-buildx-${{ github.ref_name }}
+          restore-keys: |
+            flaskr-buildx-main
+      - name: Login to GitHub Container Registry
+        uses: docker/login-action@v2
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+      - name: Build Docker image and push to GHCR
+        uses: docker/build-push-action@v4
+        with:
+          context: examples/tutorial
+          push: true
+          tags: "ghcr.io/${{ github.repository }}:${{ steps.vars.outputs.sha_short }}"
+          cache-from: type=local,src=/tmp/.buildx-cache
+          cache-to: type=local,dest=/tmp/.buildx-cache-new
+        # This ugly bit is necessary if you don't want your cache to grow forever
+        # until it hits GitHub's limit of 5GB.
+        # Temp fix
+        # https://github.com/docker/build-push-action/issues/252
+        # https://github.com/moby/buildkit/issues/1896
+      - name: Move cache
+        run: |
+          rm -rf /tmp/.buildx-cache
+          mv /tmp/.buildx-cache-new /tmp/.buildx-cache