(defun buffer-changes-recorder (change-beg change-end prev-len)
  (append-to-file
  ;(message
   (format "%s;%s;%s\n"
	   (buffer-file-name)
	   (format-time-string "%s")
	   (if (> prev-len 0)
	     (format "D;%d;%d"
		     change-beg
		     (+ change-beg prev-len))
	     (format "A;%d;%s"
		     change-beg
		     (buffer-substring change-beg change-end))
	     )
	   )
   nil "~/test.log"
   )
  )

(add-hook 'after-change-functions 'buffer-changes-recorder)