Stop presubmit_support.py from calling gcl.GetRepositoryRoot(). Instead, save the repository root in ChangeInfo and name it GetLocalRoot() to make it less confusing.
Add GetFileList() and GetFileNames() to ChangeInfo to make it less confusing and more "interface-like".

TEST=updated unit tests with a lot of pain
BUG=none

Review URL: http://codereview.chromium.org/119442

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@18266 0039d316-1c4b-4281-b951-d872f2087c98