Automatic help target using ## comments.

Makefile

help: ## Show this help message.
	echo "usage: make [target] ..."
	echo ""
	echo "targets:"
	fgrep --no-filename "##" ${MAKEFILE_LIST} | head -n '-1' | column -s ':#' -t -c 2

For example:

clean: ## Clean up the build.
    rm -rf build/*

Would output the following when calling make help:

usage: make [target] ...

targets:
clean        Clean up the build.
help         Show this help message.

How it Works

1. fgrep --no-filename "##" ${MAKEFILE_LIST}

${MAKEFILE_LIST} is a special variable that contains a list of the Makefile file names. From this we use fgrep to find all lines containing ## in the Makefiles.

2. head -n '-1'

Removes the last line of output, which is the fgrep one.

3. column -s ':#' -t -c 2

Pretty prints out the targets into columns, removing the colons and comment symbols.

And the original source of inspiration https://gist.github.com/prwhite/8168133.