anchor.diff:                  (id (htree:data history-node)) (id buffer))
             (buffer-load (url (htree:data history-node)))))))
   
  +(defun conservative-history-filter (buffer nodes)
  +  (remove-if #'(lambda (node)
  +                 (and (conservative-history-movement buffer)
  +                      (string/= (id (htree:data node)) (id buffer))))
  +             nodes))
  +
   (define-command history-backwards (&optional (buffer (current-buffer)))
     "Go to parent URL in history."
     (with-data-access (history (history-path buffer))
  -    (let ((parents (remove-if #'(lambda (node)
  -                                  (and (conservative-history-movement buffer)
  -                                       (string/= (id (htree:data node)) (id buffer))))
  -                              (htree:parent-nodes history))))
  +    (let ((parents (conservative-history-filter buffer (htree:parent-nodes history))))
         (if parents
             (set-url-from-history (first parents) buffer)
             (echo "No backward history.")))))
  
positive.code: 
  (defun history-forwards-all-suggestion-filter (&optional (buffer (current-buffer)))
    "Suggestion function over children URL from all branches."
    (let ((children (remove-if #'(lambda (node)
                                   (and (conservative-history-movement buffer)
                                        (string/= (id (htree:data node)) (id buffer))))
                               (htree:children-nodes (get-data (history-path buffer))))))
      (lambda (minibuffer)
        (if children
            (fuzzy-match (input-buffer minibuffer) children)
  
negative.code: (define-command history-forwards (&optional (buffer (current-buffer)))
    "Go to forward URL in history."
    (with-data-access (history (history-path buffer))
      (let ((children (conservative-history-filter
                       buffer (htree:children (htree:current (get-data (history-path buffer)))))))
        (if children
            (set-url-from-history (first children) buffer)
            (echo "No forward history.")))))
  
  (defun history-backwards-suggestion-filter (&optional (buffer (current-buffer)))
    "Suggestion function over all parent URLs."
    (let ((parents (conservative-history-filter
                    buffer (htree:parent-nodes (get-data (history-path buffer))))))
      (lambda (minibuffer)
        (if parents
            (fuzzy-match (input-buffer minibuffer) parents)
  