[libvirt] compressing .git/ can save 15%

Hi DV, I ran this on a fresh clone of libvirt: $ du -sh .git; git gc --aggressive; du -sh .git 54M .git ... 45M .git I propose to do the same thing on the server, libvirt.org. It's not a big deal, but decreased bandwidth wouldn't hurt, and the slightly smaller on-disk repository makes even local git tools feel a little snappier. It's worth doing for all git repositories. As far as I know, no one stores anything useful as "unlinked" commits on the server (they would be removed by the above), so there is no down-side to doing this. In fact, "man git-gc" recommends to run git gc --aggressive "every few hundred changesets or so". Adding a cron job to do it every few weeks would be nice (e.g., Sunday at 4am local). Let me know and I'll do it via my account.