locking (binary) files in git with gitolite

One of the groups at $DAYJOB indicated that lack of file locking was a
show stopper for using git itself, due to the number of binary
artefacts (images, ODTs etc) they have and the fact that prevention is
far, *far* better than cure when it comes to merging those animals :-)

Thinking about it, it struck me that most corporate setups have
exactly one canonical repo/source of truth and all devs clone
from/push to it, and so it ought to be possible to do something about
locking in this limited case.

Anyway, the end result of all this is here:
http://sitaramc.github.com/gitolite/locking.html.  You'll need the
latest tip from "master" on gitolite if you want to use it.

Hope this helps someone.  Especially if you're already using gitolite
(v3.x) it ought to be relatively painless to try out.

-- 
Sitaram