Self-documenting Makefile

Idea comes from Payton White's gist Makefile.

Enhanced by good comments from the community:

• https://gist.github.com/prwhite/8168133#gistcomment-1716694
• https://gist.github.com/prwhite/8168133#gistcomment-1737630

Usage

1. Copy help target to your Makefile.
2. Mark each Makefile target with ## comment:

target: ## This is the help line

3. Group your targets using ##@ comments:

another_target: ##@Grouped This will show up as 'Grouped targets'

other_target: ##@Grouped This will show right next to the 'another_target'

4. Use make to show help!

Usage: make [target] ...

Targets:
help      Show this help message.
target    This is the help line

Grouped targets:
another_target    This will show up as 'Grouped targets'
other_target      This will show right next to the 'another_target'