This is useful in certain (admittedly unsupported) cases 
when trying to use tools from depot_tools outside of a 
chrome repository.  In this particular case, I was trying 
to "git cl format" something that wasn't a chrome 
repository.

BUG=0

Review URL: https://codereview.chromium.org/472553003

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@289412 0039d316-1c4b-4281-b951-d872f2087c98