Summary:
Ref T13151. See PHI648. With `arc patch --nobranch`, we update submodules a little too early.
I //believe// it is safe to just update them a little later, after the intermediate branch management logic runs.
Test Plan: Ran `arc patch --nobranch`, saw submodule update run later. Not 100% sure this doesn't cause weird issues, but I can't anticipate any.
Reviewers: amckinley, jmeador
Reviewed By: jmeador
Maniphest Tasks: T13151
Differential Revision: https://secure.phabricator.com/D19475