hub is a command line tool that wraps git in order to extend it
with extra features and commands that make working with GitHub
easier.

 $ hub clone rtomayko/tilt
 # expands to:
 $ git clone git://github.com/rtomayko/tilt.git

hub is best aliased as `git', so you can type `git <command>' in the
shell and get all the usual hub features.