anchor.diff:      (lambda (minibuffer)
         (if children
             (fuzzy-match (input-buffer minibuffer) children)
  -          (error "Cannot navigate forwards.")))))
  +          (echo "Cannot navigate forwards.")))))
   
   (define-command history-forwards-query ()
     "Query forward-URL to navigate to."
  
positive.code:     (lambda (minibuffer)
        (if parents
            (fuzzy-match (input-buffer minibuffer) parents)
            (error "Cannot navigate backwards.")))))
  
  (define-command history-backwards-query ()
    "Query parent URL to navigate back to."
  
negative.code:     (lambda (minibuffer)
        (if urls
            (fuzzy-match (input-buffer minibuffer) urls)
            (echo "No history.")))))
  
  (define-command history-all-query ()
    "Query URL to go to, from the whole history."
  