anchor.diff:  type CommandType =
       | Move
       | Visual
  +    | Yank
       | Delete
       | Change
       | Go
  
positive.code:         | "d" -> Some Delete
          | "c" -> Some Change
          | "v" -> Some Visual
          | "g" -> Some Go
          | _ -> None
  
  
negative.code:             | NormalMode, [ "u" ] -> [ run Undo Nothing ]
              | NormalMode, [ "d"; "d" ] -> [ run Delete WholeLine ]
              | NormalMode, [ "c"; "c" ] -> [ run Delete WholeLine; run (SwitchMode InsertMode) Nothing ]
              | NormalMode, [ "y"; "y" ] -> [ run Yank WholeLine ]
              | NormalMode, [ "C" ] -> [ run Delete EndOfLine; run (SwitchMode InsertMode) Nothing ]
              | NormalMode, [ "D" ] -> [ run Delete EndOfLine ]
              | NormalMode, [ "x" ] -> [ run Delete CurrentLocation ]
  