Martin von Zweigbergk <martinvonz@google.com> [Fri, 29 Mar 2019 11:32:02 -0700] rev 42038
shelve: let cmdutil.revert() take care of backing up untracked files
cmdutil.revert() backs up untracked files, so I don't see a reason to
do it shelve.mergefiles(). We have tests for this and they still pass.
Differential Revision: https://phab.mercurial-scm.org/D6174