Add GitHub Actions cache support for Docker builds

- Add Docker Buildx setup to workflow
- Use GHA cache for docker builds to speed up CI
- Cache is shared across all layers and PHP versions for maximum reuse
- Conditional cache flags only apply in GitHub Actions, works locally without cache

Author: psantus

.github/workflows/deploy-docker.yml

@@ -63,6 +63,9 @@ jobs:
           php-version: 8.2
           coverage: none
 
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
       - name: Docker login
         run: echo '${{ secrets.DOCKER_PASSWORD }}' | docker login --username ${{ secrets.DOCKER_USERNAME }} --password-stdin
 

Makefile

@@ -3,9 +3,16 @@ layer ?= *
 resolve_php_versions = $(or $(php_versions),`jq -r '.php | join(" ")' ${1}/config.json`)
 resolve_tags = `./new-docker-tags.php $(DOCKER_TAG)`
 BREF_VERSION = 3
+COMMA := ,
+CACHE_FLAGS = $(if $(GITHUB_ACTIONS),--cache-from type=gha --cache-to type=gha$(COMMA)mode=max,)
 
 define build_docker_image
-	docker build -t bref/${1}-php-${2} --build-arg PHP_VERSION=${2} --build-arg BREF_VERSION=${BREF_VERSION} ${DOCKER_BUILD_FLAGS} ${1}
+	docker buildx build -t bref/${1}-php-${2} \
+		--build-arg PHP_VERSION=${2} \
+		--build-arg BREF_VERSION=${BREF_VERSION} \
+		$(CACHE_FLAGS) \
+		--load \
+		${DOCKER_BUILD_FLAGS} ${1}
 endef
 
 docker-images:
@@ -31,7 +38,7 @@ test: docker-images
 			echo "###############################################"; \
 			echo "### Testing $${dir} PHP$${php_version}"; \
 			echo "###"; \
-			docker build --build-arg PHP_VERSION=$${php_version} --build-arg TARGET_IMAGE=$${dir}-php-$${php_version} -t bref/test-$${dir}-$${php_version} tests ; \
+			docker buildx build --build-arg PHP_VERSION=$${php_version} --build-arg TARGET_IMAGE=$${dir}-php-$${php_version} -t bref/test-$${dir}-$${php_version} $(CACHE_FLAGS) --load tests ; \
 			docker run --entrypoint= --rm -v $$(pwd)/$${dir}:/var/task bref/test-$${dir}-$${php_version} /opt/bin/php /var/task/test.php ; \
 			if docker run --entrypoint= --rm -v $$(pwd)/$${dir}:/var/task bref/test-$${dir}-$${php_version} /opt/bin/php -v 2>&1 >/dev/null | grep -q 'Unable\|Warning'; then exit 1; fi ; \
 			echo ""; \