anchor.diff:  
   type CommandType =
       | Move
  -    | Select
  +    | Visual
       | Delete
       | Change
       | DoNothing
  
positive.code:         match character with
          | 'd' -> Some Delete
          | 'c' -> Some Change
          | _ -> None
  
      let keys = ResizeArray<_>()
  
negative.code:         | Delete -> 
              x.Editor.SetSelection(start, finish)
              ClipboardActions.Cut textEditorData
          | Visual ->
              x.Editor.SetSelection(start, finish)
          | _ -> ()
  
      override x.Initialize() =
  