ci: build and test each image in one job

The test job and the build job built the same image twice. Both used the
docker-container buildx driver, so each one serialized the image to a tar
stream and imported it back. On fx that export cost 3m15s of a 5m36s step,
and the gha cache gave no hits because any version bump invalidates the
single large RUN layer, while the cache export cost 81s per run.

One job now builds with the default buildx driver, which writes straight
into the local daemon, runs the smoke test, and pushes only from master.
QEMU setup is gone because every image is linux/amd64. The smoke test uses
the variant tag, so it checks the exact image that is pushed.

Expect fx to drop from about 12m to about 3m30s.

Author: f3l1x

.github/workflows/docker.yml

@@ -12,8 +12,8 @@ permissions:
   contents: read
 
 jobs:
-  test:
-    name: "Test (${{ matrix.image }})"
+  build:
+    name: "Build (${{ matrix.image }})"
     runs-on: ubuntu-latest
     strategy:
       fail-fast: false
@@ -23,56 +23,23 @@ jobs:
       - name: Checkout
         uses: actions/checkout@v6
 
-      - name: Set up Docker Buildx
-        uses: docker/setup-buildx-action@v4
-
-      - name: Build image for testing
-        uses: docker/build-push-action@v7
-        with:
-          context: ./${{ matrix.image }}
-          file: ./${{ matrix.image }}/Dockerfile
-          push: false
-          tags: dockette/coder:${{ matrix.image }}-test
-          platforms: linux/amd64
-          load: true
+      # Builds into the local Docker daemon, so no export or import step
+      - name: Build image
+        run: make build DOCKER_VARIANT=${{ matrix.image }}
 
       - name: Smoke test image
-        run: make test DOCKER_VARIANT=${{ matrix.image }} DOCKER_TAG=${{ matrix.image }}-test
-
-  build:
-    name: "Build (${{ matrix.image }})"
-    needs: test
-    runs-on: ubuntu-latest
-    strategy:
-      fail-fast: false
-      matrix:
-        image: [fx, php, nodejs, golang, python]
-    steps:
-      - name: Checkout
-        uses: actions/checkout@v6
+        run: make test DOCKER_VARIANT=${{ matrix.image }}
 
       - name: Login to DockerHub
+        if: ${{ github.ref == 'refs/heads/master' }}
         uses: docker/login-action@v4
         with:
           username: ${{ secrets.DOCKERHUB_USERNAME }}
           password: ${{ secrets.DOCKERHUB_TOKEN }}
 
-      - name: Set up QEMU
-        uses: docker/setup-qemu-action@v4
-
-      - name: Set up Docker Buildx
-        uses: docker/setup-buildx-action@v4
-
-      - name: Build and push
-        uses: docker/build-push-action@v7
-        with:
-          context: ./${{ matrix.image }}
-          file: ./${{ matrix.image }}/Dockerfile
-          push: ${{ github.ref == 'refs/heads/master' }}
-          tags: dockette/coder:${{ matrix.image }}
-          platforms: linux/amd64
-          cache-from: type=gha,scope=${{ matrix.image }}
-          cache-to: type=gha,scope=${{ matrix.image }},mode=max
+      - name: Push image
+        if: ${{ github.ref == 'refs/heads/master' }}
+        run: make push DOCKER_VARIANT=${{ matrix.image }}
 
   docs:
     name: "Docs"

Makefile

@@ -17,6 +17,10 @@ build-all:
 	$(MAKE) build DOCKER_VARIANT=golang
 	$(MAKE) build DOCKER_VARIANT=python
 
+.PHONY: push
+push:
+	docker push ${DOCKER_IMAGE}:${DOCKER_TAG}
+
 .PHONY: run
 run:
 	docker run --rm -it --platform ${DOCKER_PLATFORMS} ${DOCKER_IMAGE}:${DOCKER_TAG}