def current_line(text):
    """Return a ( <cpu number>, ( <move1>, ... ) ) tuple from text.

    If the first word of text is digits it is the CPU number.  Otherwise set
    the CPU number to None.

    """
    t = text.split(maxsplit=1)
    if t[0].isdigit():
        return t[0], ' '.join(t[1:])
    else:
        return None, text
