graft: pass 'editform' argument to 'cmdutil.getcommiteditor'

This patch passes 'editform' argument according to the format below:

  COMMAND[.ROUTE]

  - ROUTE: name of route, if there are two or more routes in COMMAND

In this patch, ROUTE is omitted.

mercurial/commands.py

@@ -3128,7 +3128,7 b' def graft(ui, repo, *revs, **opts):'
     if not opts.get('date') and opts.get('currentdate'):
         opts['date'] = "%d %d" % util.makedate()
 
-    editor = cmdutil.getcommiteditor(**opts)
+    editor = cmdutil.getcommiteditor(editform='graft', **opts)
 
     cont = False
     if opts['continue']: