anchor.diff:  ;; "open-file-function" into a download-mode slot, which is then called from
   ;; `download-open-file' with `(funcall (open-file-function download-mode)
   ;; filename).
  -(defun open-file-fn (filename)
  -  "Open `filename'.
  -`filename' is the full path of the file (or directory), as a string.
  -By default, try to open it with the system's default external program, using `xdg-open'.
  -The user can override this function to decide what to do with the file."
  -  (open-file-fn-default filename))
  +;; (defun open-file-fn (filename)
  +;;   "Open `filename'.
  +;; `filename' is the full path of the file (or directory), as a string.
  +;; By default, try to open it with the system's default external program, using `xdg-open'.
  +;; The user can override this function to decide what to do with the file."
  +;;   (open-file-fn-default filename))
   
   ;; note: put under the function definition.
  -(export '*open-file-fn*)   ;; the user is encouraged to override this in her init file.
  -(defparameter *open-file-fn* #'open-file-fn
  -  "Function triggered to open files.")
  +;; (export '*open-file-fn*)
  +;; the user is encouraged to override this in her init file.
  +;; (defparameter *open-file-fn* #'open-file-fn
  +;;   "Function triggered to open files.")
   
   (defun open-file-from-directory-completion-fn (input &optional (directory *current-directory*))
     "Fuzzy-match files and directories from `*current-directory*'."
  
positive.code:       (erase-input minibuffer)
        (update-display minibuffer))))
  
  (define-command open-file (root-mode &optional (interface *interface*))
    "Open a file from the filesystem.
  
  The user is prompted with the minibuffer, files are browsable with the
  
negative.code:   (erase-input minibuffer)
    (update-display minibuffer))
  
  (define-command enter-directory (open-file-mode &optional (minibuffer (minibuffer *interface*)))
    "If the candidate at point is a directory, refresh the minibuffer candidates with its list of files.
  
  Default keybindings: `M-Right' and `C-j'. "
  