anchor.diff:    (let ((history (buffer-history buffer)))
       (sera:and-let* ((owner (htree:owner history (id buffer)))
                       (parent-id (htree:creator-id owner)))
  -                   (gethash parent-id (buffers *browser*)))))
  +      (gethash parent-id (buffers *browser*)))))
   
   (defun buffers-with-history (history)
     "Return the list of buffers that have history HISTORY.
  
positive.code:     buffer))
  
  (define-command make-nosave-buffer (&rest args
                                            &key title modes url load-url-p)
    "Create a new buffer that won't save anything to the filesystem.
  See `make-buffer' for a description of the arguments."
    (declare (ignorable title modes url load-url-p))
  
negative.code:   "Prompt for a URL and set it in a new focused buffer."
    (let ((history (set-url-history *browser*))
          (return-actions (list (lambda-command new-buffer-load (suggestion-values)
                                  "Load URL(s) in new buffer(s)"
                                  (mapc (lambda (suggestion) (make-buffer :url (url suggestion)))
                                        (rest suggestion-values))
                                  (make-buffer-focus :url (url (first suggestion-values)))))))
      (pushnew-url-history history (url (current-buffer)))
      (prompt
       :prompt "Open URL in new buffer"
  