def METHOD_NAME(input_template_dir, source_dir):
    template_dir_filenames = os.listdir(input_template_dir)
    plain_filenames = [
        mozpath.basename(filename)
        for filename in template_dir_filenames
        if not filename.endswith(".in")
    ]
    os.makedirs(mozpath.join(source_dir, "debian"), exist_ok=True)
    for filename in plain_filenames:
        shutil.copy(
            mozpath.join(input_template_dir, filename),
            mozpath.join(source_dir, "debian", filename),
        )