def _get_revision(config):
    """
    Extracts branch and revision number from the given config parameter.
    @return: (branch, revision number)
    """
    if config.revision:
        tokens = config.revision.split(":")
        svn_branch = tokens[0]
        if len(tokens) > 1:
            revision = config.revision.split(":")[1]
        else:
            revision = "HEAD"
        return (svn_branch, revision)
    else:
        return ("trunk", "HEAD")