branchcache: unconditionally write delayed branchmap

mercurial/localrepo.py

@@ -2927,8 +2927,6 b' class localrepository:'
                 self.ui.debug(b'updating the branch cache\n')
                 self.filtered(b'served').branchmap()
                 self.filtered(b'served.hidden').branchmap()
-                # flush all possibly delayed write.
-                self._branchcaches.write_delayed(self)
 
         if repository.CACHE_CHANGELOG_CACHE in caches:
             self.changelog.update_caches(transaction=tr)
@@ -2975,6 +2973,9 b' class localrepository:'
                 filtered = self.filtered(filt)
                 self._branchcaches.update_disk(filtered)
 
+        # flush all possibly delayed write.
+        self._branchcaches.write_delayed(self)
+
     def invalidatecaches(self):
         if '_tagscache' in vars(self):
             # can't use delattr on proxy