Add --no-git argument to setup.py, recognized by ah_bootstrap - #27

@embray - this PR itself looks good, but one thing that's confusing: none of this appears in the "python setup.py --help" documentation, which is where users are going to look for this. So perhaps ah_bootstrap.py should watch for --help, and display its own help if that's given?

I'll have to think about that. As you've noticed it just nabs those options off of sys.argv. It has no interaction with distutils itself regarding command-line options. I think maybe it could insert them into distutils' argument parsing at an early stage...

👍 to --no-git. I would be in favor of merging this and opening a separate issue for the --help issue.

@embray - shall we merge this now and worry about the help option later, or do you think that should be resolved now too?

Submitted a new issue. Incidentally, I think I need to updated APE-4 regarding how issues for astropy-helpers are handled. Previously we had agreed not to use a separate issue tracker, and yet here we are doing that. I, ultimately, find this preferable actually. But as a compromise we I think we should say that users should submit issues to Astropy's main issue tracker. If an issue turns out to be something in astropy-helpers then one of use can create a separate issue here to track it.

In other words, we wouldn't advertise this issue tracker to users. (Though if developers and more savvy users find this one and report astropy-helpers issues directly to it there's no harm in that either).