mercurial/dirstate.py

--- a/mercurial/dirstate.py	Sat Oct 20 19:13:05 2018 +0900
+++ b/mercurial/dirstate.py	Sat Oct 20 17:56:00 2018 +0900
@@ -317,7 +317,7 @@
         return copies
 
     def setbranch(self, branch):
-        self._branch = encoding.fromlocal(branch)
+        self.__class__._branch.set(self, encoding.fromlocal(branch))
         f = self._opener('branch', 'w', atomictemp=True, checkambig=True)
         try:
             f.write(self._branch + '\n')