anchor.diff:  
               /// Invoked when the user requests auto-completion using the tab character
               [<DefaultValue>]
  -            val mutable public AutoCompleteEvent : AutoCompleteHandler
  +            val mutable public AutoCompleteEvent : AutoCompleteHandler option
   
               let mutable handlers : Handler array = Array.zeroCreate 0
   
  
positive.code:             member private x.CmdTabOrComplete () =
                  let mutable complete = false;
  
                  if x.AutoCompleteEvent <> null then
                      if x.TabAtStartCompletes then
                          complete <- true
                      else 
  
negative.code:             | Forward = 1
              | Backward = 2
  
          type Handler(cmd : Command, keyInfo : ConsoleKeyInfo, h : KeyHandler) =
              member val HandledCommand = cmd
              member val KeyInfo = keyInfo
              member val KeyHandler = h
  
              new(cmd : Command, key, h : KeyHandler) = Handler(cmd, new ConsoleKeyInfo((char) 0, key, false, false, false), h)
              new(cmd : Command, c, h : KeyHandler) = Handler(cmd, new ConsoleKeyInfo (c, ConsoleKey.Zoom, false, false, false), h)
              
              static member Alt cmd c k h = Handler (cmd, new ConsoleKeyInfo (c, k, false, true, false), h)
              static member Control cmd (c : char) h = Handler (cmd, (char) ((int)c - (int)'A' + 1), h)
  