Makefile: auto-incrementing

gistfile1.txt

IMAGE_NAME := whatever/whatever

.PHONY: docker-build version-increment bc-check
docker-build: version-increment
	DOCKER_BUILDKIT=1 docker buildx build -t $(IMAGE_NAME):v$(shell cat version.txt) .

version-increment: bc-check
	bc <<< "1 + $(shell cat version.txt)" > version.txt

bc-check:
	@command -v bc >/dev/null 2>&1 || { echo >&2 "I require bc but it's not installed. Aborting."; exit 1; }