It's very rarely needed anyway but enter_chroot does everything under the sun.
Avoids:
error: could not lock config file ~/.gitconfig
Change-Id: Ide72b14fd434b182a88d2fc636559b3515905509
BUG=chromium-os:11523
TEST=Ran it ... 10x
Review URL: http://codereview.chromium.org/6312069