anchor.diff:    `(keybind ,key ,start ,dst
               ,commands
               (,(cond ((null message)
  -                     `(echo (:lisp (secho-arg (default-message
  -                                                ',dst
  -                                                ,(com-stringify-form (car commands)))))))
  +                     `(hardstatus string
  +                                  (:lisp (sstringarg (default-message
  +                                                      ',dst
  +                                                      ,(com-stringify-form (car commands)))))))
                       ((zerop (length message)) ())
  -                    (t `(echo (:lisp (secho-arg ,message))))))))
  +                    (t `(hardstatus string (:lisp (sstringarg ,message))))))))
   
   (keybind-common j snormal snormal ((focus down)))
   (keybind-common k screen raw ((focus up)) "focus up")
  
positive.code:     with quote."
    (concat-str "'" str "'"))
  
  (defun secho-arg (str)
    " An argument for echo command of screeen must be wrapped
      with double quote."
    (concat-str "\"" str "\""))
  
  (defun state-leave-desc (state)
  
negative.code: ; a form generates the message
  (keybind-common l snormal snormal ((focus right)) (coerce (coerce "focus right" 'list) 'string))
  (keybind-common l snormal snormal ((focus right)) "")
  (keybind-common ^z raw screen ())
  
  (defun normalize-cmd-format (cmd)
    (cond ((null cmd) '())
  