Self-documenting Makefile

example.txt

$ make help
target                         help
------                         ----
foo                            this is a doc 

Makefile

SHELL := /bin/bash

foo: ## this is a doc
	echo "foo"

.DEFAULT_GOAL := help
.PHONY: help
help:
	@IFS=$$'\n' ;								\
	help_lines=(`fgrep -h "##" $(MAKEFILE_LIST)				\
			| fgrep -v fgrep					\
			| grep -v '^\#'						\
			| sed -e 's/\\$$//'					\
			| sed -e 's/\#\#/:/'`);					\
	printf "%-30s %s\n" "target" "help" ;					\
	printf "%-30s %s\n" "------" "----" ;					\
	for help_line in $${help_lines[@]}; do					\
	    IFS=$$':' ;								\
	    help_split=($$help_line) ;						\
	    help_command=`							\
		echo $${help_split[0]}						\
		| sed -e 's/^ *//' -e 's/ *$$//'`;				\
	    help_info=`								\
		echo $${help_split[2]}						\
		| sed -e 's/^ *//' -e 's/ *$$//'`;				\
	    printf "\033[36m%-30s\033[0m%s %s\n" $$help_command $$help_info;	\
	done