This patch fixes the implementation as follows:

  1/ Fix '--full' option to check for all changes in the
     current branch relative to upstream. The old code only
     considered currently modified files, which made little
     sense.

  2/ Fix '--full' option to apply Chromium style too.

  3/ Use a proper source file filter. The original code used
     ".*.cc .*.cpp .*.h" as the filter, which didn't catch anything !?

  4/ Add --no-ext-diff to make it work with custom "git diff" handlers.

R=agable@chromium.org, maruel@chromium.org, pliard@chromium.org
BUG=NONE

Review URL: https://chromiumcodereview.appspot.com/14942012

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@200832 0039d316-1c4b-4281-b951-d872f2087c98