Pierre-Yves David <pierre-yves.david@octobus.net> [Tue, 24 Aug 2021 21:16:48 +0200] rev 47916
dirstate: drop the `_merge` method
It only has one caller that only use one of the branch, so lets inline that
branch and clean things up further.
Differential Revision: https://phab.mercurial-scm.org/D11351