For a bot_update Git world, we don't really want to commit patches.  Instead
we just want to leave them unstaged.

BUG=370503
TEST=ran locally with and without flag

Review URL: https://codereview.chromium.org/273543002

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@269468 0039d316-1c4b-4281-b951-d872f2087c98