make recipe to tag docker images with git tags

makefile

### example for setting up a make workflow that can tag images based on the git tag
### the trailing ; are important: runs the commands in the same "shell" and the $$tag variable flows through

docker-build:
	@echo "Latest 3 tags: "; \
	git ls-remote --sort='v:refname' --tags ./. | tail -n 3; \
	read -p "Enter New Tag:" tag; \
	echo "Releasing new tag: $$tag"; \
	git tag $$tag; \
	git push origin $$tag -f; \
	docker build . -f Dockerfile \
		-t foo:latest \
		-t foo:$$tag;

docker-push:
	@tag=$$(git ls-remote --sort='v:refname' --tags ./. | awk -F/ '{print $$3}' | tail -n 1); \
	echo "Pushing tag: $$tag to docker"; \
	docker push foo:latest; \
	docker push foo:$$tag;