commitablectx: move extra from workingctx

mercurial/context.py

@@ -991,6 +991,8 b' class commitablectx(basectx):'
         return encoding.tolocal(self._extra['branch'])
     def closesbranch(self):
         return 'close' in self._extra
+    def extra(self):
+        return self._extra
 
 class workingctx(commitablectx):
     """A workingctx object makes access to data related to
@@ -1018,9 +1020,6 b' class workingctx(commitablectx):'
             p = p[:-1]
         return [changectx(self._repo, x) for x in p]
 
-    def extra(self):
-        return self._extra
-
     def tags(self):
         t = []
         for p in self.parents():