Most users of repo are also using Gerrit Code Review, and will want
the commit-msg hook to be automatically installed into their local
projects so that Change-Ids are assigned when commits are created,
not when they are first uploaded.
(cherry picked from commit a949fa5d20
but squashed with latest hook script from version 2.1.2)
Change-Id: Ie68b2d60ac85d8c2285d2e1e6a4536eb76695547
Signed-off-by: Shawn O. Pearce <sop@google.com>