Split out parser generation into a separate function

rust2rpm/__main__.py

@@ -412,9 +412,7 @@ def exit_on_common_errors():
     except FileNotFoundError as e:
         sys.exit(str(e))
 
-
-@exit_on_common_errors()
-def main():
+def get_parser():
     default_target = get_default_target()
 
     parser = argparse.ArgumentParser("rust2rpm",
@@ -461,6 +459,13 @@ def main():
                                       "path/to/project/",
                         nargs="?")
     parser.add_argument("version", nargs="?", help="crates.io version")
+
+    return parser
+
+
+@exit_on_common_errors()
+def main():
+    parser = get_parser()
     args = parser.parse_args()
 
     if args.show_license_map: