Fetching tarball of a commit

[Sean Farley]

> I saw that but I don't quite follow what it provides.  Could you show sample
> output?

Ok, Ryan, what direction do you want the github portgroup to go in?

1) Have the portfile maintainer specify a git hash via git.branch (or
git.tag; whichever one it is)?

ex.

git.branch 9ccfac11f31d8d05d48092efcbec8015c68f6cc1
github.setup MythTV mythtv 0.25-8

2) Have the maintainer override the version?

github.setup MythTV mythtv 9ccfac11f31d8d05d48092efcbec8015c68f6cc1
version 0.25-8

3) Something else entirely?