ci: try faster build

.github/workflows/build-and-publish.yml

@@ -8,6 +8,9 @@ name: "Build, Test and Publish"
   # run it during pull request
   pull_request:
 
+env:
+  IMAGE_NAME: glenux/teaching-boilerplate
+
 jobs:
   build-docker-image:
     name: "Build docker image"
@@ -24,21 +27,14 @@ jobs:
       - name: Checkout code
         uses: actions/checkout@v2
 
-      - name: Set up Docker Buildx
-        id: buildx
-        uses: docker/setup-buildx-action@v1
-
       - name: Build image and save as file
-        uses: docker/build-push-action@v2
-        with:
-          # relative path to the place where source code with Dockerfile
-          # is located
-          context: .
-          file: docker/Dockerfile
-          # Note: tags has to be all lower-case
-          tags: |
-            glenux/teaching-boilerplate:latest
-          outputs: type=docker,dest=/tmp/teaching-boilerplate.image.tar
+        run: |
+          docker build \
+            --cache-from $IMAGE_NAME:latest \
+            --tag $IMAGE_NAME:latest \
+            --build-arg BUILDKIT_INLINE_CACHE=1 \
+            "."
+          docker save $IMAGE_NAME:latest > /tmp/image.tar
 
       - name: Image digest
         run: echo ${{ steps.docker_build.outputs.digest }}
@@ -48,12 +44,12 @@ jobs:
           echo "BUILD_VERSION=$BUILD_VERSION" >> /tmp/extra.env
           cat /tmp/extra.env
 
-      - name: Upload artifact
+      - name: Upload artifacts
         uses: actions/upload-artifact@v2
         with:
-          name: teaching-boilerplate-image
+          name: artifacts
           path: |
-            /tmp/teaching-boilerplate.image.tar
+            /tmp/image.tar
             /tmp/extra.env
 
   test-docker-image:
@@ -68,7 +64,7 @@ jobs:
       - name: Download artifact
         uses: actions/download-artifact@v2
         with:
-          name: teaching-boilerplate-image
+          name: artifacts
           path: /tmp
 
       - name: Load environment
@@ -77,7 +73,7 @@ jobs:
 
       - name: Load image
         run: |
-          docker load --input /tmp/teaching-boilerplate.image.tar
+          docker load --input /tmp/image.tar
           docker image ls -a
 
       - name: Build HTML for docs
@@ -101,7 +97,7 @@ jobs:
       - name: Download artifact
         uses: actions/download-artifact@v2
         with:
-          name: teaching-boilerplate-image
+          name: artifacts
           path: /tmp
 
       - name: Load environment
@@ -114,7 +110,7 @@ jobs:
 
       - name: Load image
         run: |
-          docker load --input /tmp/myimage.tar
+          docker load --input /tmp/image.tar
           docker image ls -a
 
       - name: Login to DockerHub