Add arg to specify borg program

backup.py

@@ -191,9 +191,11 @@ def main(argv: list[str]):
         description="Back up the local system using borg",
         formatter_class=argparse.ArgumentDefaultsHelpFormatter)
 
-    default_config = str(pathlib.Path(__file__).parent / "config.yaml")
+    base = pathlib.Path(__file__).parent
     parser.add_argument('-c', '--config',
-                        help="Config file", default=default_config)
+                        help="Config file", default=str(base / "config.yaml"))
+    parser.add_argument('-b', '--borg',
+                        help="Borg command", default=str(base / "borg.sh"))
     parser.add_argument('-n', '--dry-run', action="store_true",
                         help="Just print filenames, don't run borg")