vim-patch:7.4.308 #832

Problem:    When using ":diffsplit" on an empty file the cursor is displayed
            on the command line.
Solution:   Limit the value of w_topfill.

https://code.google.com/p/vim/source/detail?r=e3d2b8d83bb30c428a051f50791e454fcbc080af

src/nvim/diff.c

@@ -598,6 +598,7 @@ static void diff_redraw(int dofold)
         } else if ((n > 0) && (n > wp->w_topfill)) {
           wp->w_topfill = n;
         }
+        check_topfill(wp, FALSE);
       }
     }
   }