Better documentation for `space_for_menu`.

IPython/terminal/interactiveshell.py

@@ -102,7 +102,11 b' class TerminalInteractiveShell(InteractiveShell):'
     mime_renderers = Dict().tag(config=True)
 
     space_for_menu = Integer(6, help='Number of line at the bottom of the screen '
-                                     'to reserve for the completion menu'
+                                     'to reserve for the tab completion menu, '
+                                     'search history, ...etc, the height of '
+                                     'these menus will at most this value. '
+                                     'Increase it is you prefer long and skinny '
+                                     'menus, decrease for short and wide.'
                             ).tag(config=True)
 
     pt_app = None