diff -r 0903d6b9b1df -r 3e91d9978bec mercurial/localrepo.py
--- a/mercurial/localrepo.py	Tue Jan 19 00:20:53 2021 +0100
+++ b/mercurial/localrepo.py	Fri Jan 15 01:58:59 2021 +0100
@@ -2063,7 +2063,7 @@
         return self._revbranchcache
 
     def register_changeset(self, rev, changelogrevision):
-        pass
+        self.revbranchcache().setdata(rev, changelogrevision)
 
     def branchtip(self, branch, ignoremissing=False):
         """return the tip node for a given branch