help: provide a more helpful message when no keyword are matched Before this changeset, when no topic were matching the provided keyword ( in command such as `hg help --keyword babar`) the output was empty. This is confusing and unhelpful for new users seeking assistance in the help. We now display: $ hg help --keyword babar abort: no matches (try "hg help" for a list of topics) This send users in a new direction where they may find what they are looking for.

--- a/tests/test-help.t	Tue Apr 29 11:40:42 2014 -0700
+++ b/tests/test-help.t	Wed Apr 16 20:01:03 2014 -0400
@@ -988,6 +988,13 @@
   
    qclone clone main and patch repository at same time
 
+Test unfound keyword
+
+  $ hg help --keyword nonexistingwordthatwillneverexisteverever
+  abort: no matches
+  (try "hg help" for a list of topics)
+  [255]
+
 Test omit indicating for help
 
   $ cat > addverboseitems.py <<EOF