github port group

[Sean Farley]

> I remembered that I downloaded a .tar.gz of a revision of some project from github in October 2011. I tried downloading the same revision now, and to my surprise, found both the old and the new .tar.gz archives to have the same checksums. So either github is using exorbitant amounts of disk space to keep these old archives around, or has installed a custom version of gzip whose random seed can be controlled or by some other means ensure that the gzip output of repeated runs is identical. That's good news, so I suppose we can indeed fix the github portgroup now to fetch distfiles even when git.branch is specified.

Ok, I can start updating my patch for that.

> We have most definitely observed the effect I described, however, with bitbucket:
>
> https://trac.macports.org/ticket/30241
>
> https://trac.macports.org/ticket/32833
>
> https://trac.macports.org/ticket/32791
>
> Bitbucket archives also seem to sometimes change for reasons other than entropy:
>
> https://trac.macports.org/ticket/27843

I think it's an effect of mercurial rather than bitbucket itself.
Mercurial puts a .hg_archival.txt into the tarball by default which
changes if a repo adds any tags.

> We could perhaps open a dialog with the people at bitbucket and see if this can be changed.

They would need to either 1) remove the .hg* files (usually just
.hg_archival.txt and .hgtags) for all 'hg archive' commands, or 2)
make a new url http://bitbucket.org/user/project/get/no_hg_dot_files/<changeset>.tar.gz

I dunno if they'd be willing to do either, but doesn't hurt to ask.