anchor.diff:    (with-result (entry (read-from-minibuffer
                          (make-instance 'minibuffer
                                         :input-prompt "Open bookmark:"
  -                                      :completion-function #'bookmark-completion-filter)))
  +                                      :completion-function (bookmark-completion-filter))))
       ;; TODO: Add support for multiple bookmarks?
       (set-url (url entry) :buffer (current-buffer) :raw-url-p t)))
   
  
positive.code:                          (make-instance 'minibuffer
                                          :input-prompt "Delete bookmark(s):"
                                          :multi-selection-p t
                                          :completion-function #'bookmark-completion-filter)))
      (setf (bookmarks-data *interface*)
            (set-difference (bookmarks-data *interface*) entries :test #'equals))))
  
  
negative.code:       (setf (tags entry) (sort tags #'string<))
        (push entry (bookmarks-data *interface*)))))
  
  (defun bookmark-completion-filter ()
    (lambda (input)
      (let ((validator (tag-specification-validator (parse-tag-specification
                                                     (str:replace-all " " " " input))))
            (bookmarks (bookmarks-data *interface*)))
        (when validator
          (setf bookmarks (remove-if (lambda (bookmark)
                                       (not (funcall validator
                                                     (tags bookmark))))
                                     bookmarks)))
        (fuzzy-match input bookmarks))))
  
  (defun tag-completion-filter (&key with-empty-tag)
    "When with-empty-tag is non-nil, insert the empty string as the first tag.
  