def split_treetag(path):
    """split a path into head,treetag.

    A path like /opt/Epics/R3.14.8/support/BIIcsem/1-0+001
    is splitted to
    "/opt/Epics/R3.14.8/support/BIIcsem/1-0","001"

    Here is an example:
    >>> split_treetag("abc/def/1-0")
    ['abc/def/1-0', '']
    >>> split_treetag("abc/def/1-0+001")
    ['abc/def/1-0', '001']
    """
    l = path.rsplit('+', 1)
    if len(l) < 2:
        l.append('')
    return l
