This time, do not use the --config-dir hack on svn < 1.7 for the diff command
that runs against a remote URL.  This seems to trigger auth prompts (see revert
comments on https://codereview.chromium.org/14297017/ ).

Review URL: https://chromiumcodereview.appspot.com/14084009

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@196263 0039d316-1c4b-4281-b951-d872f2087c98