def do_create(marfile, files, compress, productversion=None, channel=None,
              signing_key=None, signing_algorithm=None):
    """Create a new MAR file."""
    with open(marfile, 'w+b') as f:
        with MarWriter(f, productversion=productversion, channel=channel,
                       signing_key=signing_key,
                       signing_algorithm=signing_algorithm,
                       ) as m:
            for f in files:
                m.add(f, compress=compress)
Create a new MAR file.