anchor.diff:  (define-handler (js/notebook-selector.js :content-type "application/javascript") ()
     (ps
       (defvar *current-fs-listing* nil)
  +
  +    (defun common-prefix-of (starting-point strings)
  +      (let ((max-prefix (loop for s in strings minimize (length s)))
  +            (same-at? (lambda (ix)
  +                        (let ((chr (aref strings 0 ix))
  +                              (res t))
  +                          (loop for s in strings unless (string= (aref s ix) chr) do (setf res f))
  +                          res))))
  +        (+ starting-point
  +           (join
  +            (loop for i from (length starting-point) to max-prefix
  +               when (same-at? i) collect (aref strings 0 i))))))
   
       (defun notebook-link-template (notebook current-notebook-id)
         (if (equal? current-notebook-id (@ notebook :path))
  
positive.code:                 (fnames (map (lambda (d) (@ d :string)) (@ filtered :files)))
                  (dirnames (map (lambda (d) (@ d :string)) (@ filtered :directories)))
                  (key-code (@ event key-code)))
             (console.log "KEY CODE" key-code)
             (cond
               ((= 9 key-code)
                (chain event (prevent-default))
                (chain elem (focus))
                (console.log "FOUND TAB KEYPRESS" "TODO"))
               ((and (= 13 key-code) (member? val fnames))
                (setf (@ window location href) (+ "/#book=" val)))
               ((and (= 13 key-code) (member? dval dirnames))
                (filesystem! (by-selector ".filesystem-view") dval))
               ((or (= 8 key-code) (= 46 key-code))
                (console.log "FOUND DELETING NON-CHAR KEYPRESS" key-code "RE-RUNNING ls REQUEST")
                (filesystem!
                 (by-selector ".filesystem-view")
                 (+ (chain val (split "/") (slice 0 -1) (join "/")) "/")
  
negative.code:                 (cond
                    ((and (= (length (@ filtered :directories)) 1)
                          (= (length (@ filtered :files)) 0))
                     (setf (@ elem value) (@ filtered :directories 0 :string))
                     (filesystem! (by-selector ".filesystem-view") (@ filtered :directories 0 :string)))
                    ((and (= (length (@ filtered :directories)) 0)
  