svn diff would only generate a diff for modified files but the current code
would not respect full_move=True. full_move=True is necessary to make it work on
the try server.

TEST=svn move chrome chrome2; echo foo>>PRESUBMIT.py
The try job should fail but the diff should be right.
BUG=none

Review URL: http://codereview.chromium.org/1965001

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@46566 0039d316-1c4b-4281-b951-d872f2087c98