makefile: support arm64, suggest `git tag` command on `make docker-push`

Makefile

@@ -1,6 +1,9 @@
+# sync with https://github.com/fphammerle/switchbot-mqtt/blob/master/Makefile
+
 DOCKER_IMAGE_NAME := fphammerle/systemctl-mqtt
 DOCKER_TAG_VERSION := $(shell git describe --match=v* --dirty | sed -e 's/^v//')
 ARCH := $(shell arch)
+DOCKER_TAG_ARCH_SUFFIX_aarch64 := arm64
 DOCKER_TAG_ARCH_SUFFIX_armv6l := armv6
 DOCKER_TAG_ARCH_SUFFIX_x86_64 := amd64
 DOCKER_TAG_ARCH_SUFFIX = ${DOCKER_TAG_ARCH_SUFFIX_${ARCH}}
@@ -13,3 +16,4 @@ docker-build:
 
 docker-push: docker-build
 	sudo docker push "${DOCKER_IMAGE_NAME}:${DOCKER_TAG}"
+	@echo git tag --sign --message '$(shell sudo docker image inspect --format '{{join .RepoDigests "\n"}}' "${DOCKER_IMAGE_NAME}:${DOCKER_TAG}")' docker/${DOCKER_TAG} $(shell git rev-parse HEAD)