Add current directory into load-path in Emacs

Useful when developing emacs plugin:

(defun add-pwd-into-load-path ()
  "add current directory into load-path, useful for elisp developers"
  (interactive)
  (let ((dir (expand-file-name default-directory)))
    (if (not (memq dir load-path))
        (add-to-list 'load-path dir)
        )
    (message "Directory added into load-path:%s" dir)
    )
  )