The Git project has a patch submission process
that's unfamilar to the majority of Git users. Any potential
contributor—wanting to fix a small bug, or tweak documentation
to make it more friendly—will learn that mailing a patch is
not as simple as you might expect,
especially if they're using a webmail service, like Gmail. The
recommended approach is to forgo regular email clients, and
on the command-line to ensure nothing gets lost or auto-bounced
(for containing HTML, for instance, which Gmail does by default).
This might change in the future, but for the moment, the core Git contributors have decided to keep patch review where it is, on the mailing list, and won't be reviewing, for instance, GitHub or Bitbucket pull requests.
submitGit is a small step in trying to make patch submission easier. If you create a pull request on github.com/git/git/, submitGit can send it to the mailing list for you, correctly formatting the patches. The discussion stays where it is—on the list—but at least that initial step is a little easier.