--- a/hgext3rd/topic/__init__.py	Thu Aug 11 22:52:49 2016 +0200
+++ b/hgext3rd/topic/__init__.py	Fri Aug 12 11:09:26 2016 +0200
@@ -268,6 +268,13 @@
         marker = '*' if t == current else ' '
         ui.write(' %s %s\n' % (marker, t))
 
+@command('stack [TOPIC]', [] + commands.formatteropts)
+def cmdstack(ui, repo, topic='', **opts):
+    """list all changesets in a topic
+
+    List the current topic by default."""
+    return stack.showstack(ui, repo, topic, opts)
+
 def summaryhook(ui, repo):
     t = repo.currenttopic
     if not t: