def get_dir_from_zipfile(zip_file, fallback=None):
    """Return the name of the root folder in a zip file.

    :param zip_file: a :class:`zipfile.ZipFile` instance.
    :param fallback: if `None`, the name of the zip file is used. This is
        returned if the zip file contains more than one top-level directory,
        or none at all.
    """
    fallback = fallback or zip_file.filename
    directories = [name for name in zip_file.namelist() if name.endswith("/")
                   and len(PurePath(name).parts) == 1]
    return fallback if len(directories) > 1 else directories[0]
def _expandsets(kindpats, ctx):
    """Returns the kindpats list with the 'set' patterns expanded."""
    fset = set()
    other = []

    for kind, pat, source in kindpats:
        if kind == "set":
            if not ctx:
                raise error.ProgrammingError("fileset expression with no " "context")
            s = ctx.getfileset(pat)
            fset.update(s)
            continue
        other.append((kind, pat, source))
    return fset, other