anchor.diff:    (when (multi-selection-p minibuffer)
       (with-slots (completions marked-completions) minibuffer
         (setf marked-completions (set-difference marked-completions completions)))
  +    (state-changed minibuffer)
       (update-display minibuffer)))
  
positive.code:   (when (multi-selection-p minibuffer)
      (with-slots (completions marked-completions) minibuffer
        (setf marked-completions (union completions marked-completions)))
      (update-display minibuffer)))
  
  (define-command minibuffer-unmark-all (&optional (minibuffer (current-minibuffer)))
  
negative.code: (defmethod set-completions ((minibuffer minibuffer) completions)
    "Set the completions and update the display."
    (setf (completions minibuffer) completions)
    (state-changed minibuffer)
    (update-display minibuffer))
  
  @export
  