diff -r 1c6f7cc52da9 -r 69da16b366ad mercurial/commands.py
--- a/mercurial/commands.py	Thu Sep 10 10:48:20 2015 -0400
+++ b/mercurial/commands.py	Thu Sep 10 20:22:37 2015 -0400
@@ -3942,9 +3942,9 @@
 @command('help',
     [('e', 'extension', None, _('show only help for extensions')),
      ('c', 'command', None, _('show only help for commands')),
-     ('k', 'keyword', '', _('show topics matching keyword')),
+     ('k', 'keyword', None, _('show topics matching keyword')),
      ],
-    _('[-ec] [TOPIC]'),
+    _('[-eck] [TOPIC]'),
     norepo=True)
 def help_(ui, name=None, **opts):
     """show help for a given topic or a help overview