Added __main__.py meaning the sdbus module can be executed

Only one command available right now "gen-from-files" which
generates the interface classes from the given XML introspection
file. (usually under /usr/share/dbus-1/interfaces/)

src/sdbus/__main__.py

@@ -0,0 +1,62 @@
+# SPDX-License-Identifier: LGPL-2.1-or-later
+
+# Copyright (C) 2020, 2021 igo95862
+
+# This file is part of python-sdbus
+
+# This library is free software; you can redistribute it and/or
+# modify it under the terms of the GNU Lesser General Public
+# License as published by the Free Software Foundation; either
+# version 2.1 of the License, or (at your option) any later version.
+
+# This library is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# Lesser General Public License for more details.
+
+# You should have received a copy of the GNU Lesser General Public
+# License along with this library; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301 USA
+from __future__ import annotations
+
+from argparse import ArgumentParser, Namespace
+from pathlib import Path
+from typing import List
+
+from .interface_generator import (DbusInterfaceIntrospection,
+                                  generate_async_py_file, interfaces_from_file)
+
+
+def run_gen_from_file(namespace: Namespace) -> None:
+    interfaces: List[DbusInterfaceIntrospection] = []
+
+    for file in namespace.filenames:
+        interfaces.extend(interfaces_from_file(file))
+
+    print(
+        generate_async_py_file(
+            interfaces, namespace.no_imports_header))
+
+
+def generator_main() -> None:
+
+    main_arg_parser = ArgumentParser()
+    subparsers = main_arg_parser.add_subparsers()
+
+    generate_from_file_parser = subparsers.add_parser('gen-from-file')
+    generate_from_file_parser.set_defaults(func=run_gen_from_file)
+
+    generate_from_file_parser.add_argument(
+        'filenames', type=Path, nargs='+')
+
+    generate_from_file_parser.add_argument(
+        '--no-imports-header', action='store_false', default=True,
+        help="Do NOT include 'import' header",
+    )
+
+    args = main_arg_parser.parse_args()
+    args.func(args)
+
+
+if __name__ == "__main__":
+    generator_main()