diff -r 65fd9f2982b4 -r 1d1f8f56daac hgext3rd/topic/common.py
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/hgext3rd/topic/common.py	Thu Apr 18 11:12:58 2019 +0200
@@ -0,0 +1,8 @@
+# Copyright 2019 Pierre-Yves David <pierre-yves.david@octobus.net>
+#
+# This software may be used and distributed according to the terms of the
+# GNU General Public License version 2 or any later version.
+
+def hastopicext(repo):
+    """True if the repo use the topic extension"""
+    return getattr(repo, 'hastopicext', False)