status: advertise --abort instead of 'update -C .' to abort graft

Recent release got us a --abort flag for 'hg graft' command which is nice UI and
we should advertise that to stop the graft instead of 'update -C .' which is
kind of ugly.

Differential Revision: https://phab.mercurial-scm.org/D4169

mercurial/cmdutil.py

@@ -613,7 +613,7 b' def _updatecleanmsg(dest=None):'
 
 def _graftmsg():
     # tweakdefaults requires `update` to have a rev hence the `.`
-    return _helpmessage('hg graft --continue', _updatecleanmsg())
+    return _helpmessage('hg graft --continue', 'hg graft --abort')
 
 def _mergemsg():
     # tweakdefaults requires `update` to have a rev hence the `.`

tests/test-graft.t

@@ -237,7 +237,7 b' Using status to get more context'
   # To mark files as resolved:  hg resolve --mark FILE
   
   # To continue:    hg graft --continue
-  # To abort:       hg update --clean . (warning: this will discard uncommitted changes)
+  # To abort:       hg graft --abort
   
 
 Commit while interrupted should fail: