create hardlink for the directory (includes childs).

def create_hardlink(self, dest_path: str):
        ''' create hardlink for the directory (includes childs). '''

        # self
        dirinfo = DirectoryInfo(dest_path)
        dirinfo.ensure_created()

        # child
        for item in self.list_items():
            item.create_hardlink(os.path.join(dest_path, item.path.name))