Update digest with the file content by path.

        :param path:
        :return:

def add(self, path):
        '''
        Update digest with the file content by path.

        :param path:
        :return:
        '''
        with salt.utils.files.fopen(path, 'rb') as ifile:
            for chunk in iter(lambda: ifile.read(self.__buff), b''):
                self.__digest.update(chunk)