set default file encoding to utf-8

There's no reason to support any other encoding in these files.
This only affects the files themselves and not streams they open.

Bug: https://crbug.com/gerrit/10418
Change-Id: I053cb40cd3666ce5c8a0689b9dd938f24ca765bf
diff --git a/subcmds/branches.py b/subcmds/branches.py
index fa1dff6..fb60d7d 100644
--- a/subcmds/branches.py
+++ b/subcmds/branches.py
@@ -1,3 +1,4 @@
+# -*- coding:utf-8 -*-
 #
 # Copyright (C) 2009 The Android Open Source Project
 #