anchor.diff:                          (multiple-value-list (realize-gesture-spec :keyboard gesture))))
              (in-table (position gesture keystroke-accelerators :test #'equal)))
         (when (and in-table errorp)
  -        (error 'command-already-present))
  +        (error 'command-already-present :command-table-name
  +               (command-table-designator-as-name table)))
         (if in-table
   	  (setf (nth in-table keystroke-items) item)
   	  (progn
  
positive.code:   (let* ((table (find-command-table command-table))
  	 (old-item (find-menu-item string command-table :errorp nil)))
      (cond ((and errorp old-item)
  	   (error 'command-already-present))
  	  (old-item
  	   (remove-menu-item-from-command-table command-table string))
  	  (t nil))
  
negative.code:   (unless inherit-from
      (setq inherit-from '(global-command-table)))
    (if (and name errorp (gethash name *command-tables*))
        (error 'command-table-already-exists :command-table-name name)
        (let ((result (make-instance 'standard-command-table :name name
  	                 :inherit-from inherit-from
  	                 :menu (menu-items-from-list menu))))
  