This is breaking the ability to specify an alternate DEPS file, and do
things like sync release tags where DEPS is still from svn and we need
.DEPS.git to do a git checkout.

R=iannucci@chromium.org, szager@chromium.org
BUG=407049

Review URL: https://codereview.chromium.org/511533003

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@291665 0039d316-1c4b-4281-b951-d872f2087c98