Add a super nice help documentation to any Makefile

makefile_help.mk

# Add this to your Makefile or include it as a separate .mk
# to generate instant professional-looking documentation for your Make
# targets.
#
# To add documentation for a target name, add a ## comment after the _first_ definition of that target.
# To add documentation for environment variables, add a ## comment after the _first_ definition of that environment variable.
# To see the docs, run: make usage.
#
# Inspired by: http://marmelab.com/blog/2016/02/29/auto-documented-makefile.html
PROJECT_NAME ?= example ## Defines the name of your project.

usage: ## Prints this help text.
	printf "make [target]\n \
\n\
Hack on $(PROJECT_NAME).\n \
\n\
TARGETS\n\n\
$$($(MAKE) generate_target_docs)\n\n\
ENVIRONMENT VARIABLES\n\n\
$$($(MAKE) generate_env_var_docs)\n\n\
"

test_target: ## A test to show that this mk works.
  echo 'It works!'

generate_target_docs:
	fgrep -h '##' $(MAKEFILE_LIST) | \
		fgrep -v '?=' | \
		fgrep -v gre | \
		sed 's/\\$$//' | \
		sed -e 's/##//' | \
		grep -v 'sed' | \
		sort -u | \
		awk -F': +' '{printf"%-5s%-20s%s\n","",$$1,$$2}'

generate_env_var_docs:
	fgrep '?=' $(MAKEFILE_LIST) | \
		grep -v grep | \
		sed 's/\?=.*##/;/' | \
		grep -v sed |  \
		sort -u | \
		awk -F' ; ' '{printf"%-5s%-20s%s\n","",$$1,$$2}'