Second--I grabbed the libdrm 2.4.31 tarball, rather than using git.
If you follow the link I mentioned (http://forums.debian.net/viewtopic.php?f=16&t=68862), I mentioned what worked for me.
I said "Squeeze" there, but it should be enough info to get any Debian version running Mesa from git.
(Whizse's tip is probably better than what I did, though)
If you use the Debian forums, I'd be happy to open that thread up to anything related to Mesa from git (whether it's enabling pipe-video, tracking 8.0, using clover, or whatever else)
Also...Debian Wheezy or later has gcc-4.6, which you need if you want Clover. That might be interesting.