make: add helper to rebase local branches to incorporate upstream changes

backup.py

@@ -284,7 +284,7 @@ def main(argv: list[str]):
                 backup.run(out)
         sys.stdout.flush()
     else:
-        borg = subprocess.Popen([args.borg,
+        borg = subprocess.Popen([borg,
                                  "create",
                                  "--verbose",
                                  "--list",
@@ -386,7 +386,7 @@ def main(argv: list[str]):
                 summary = warnmsg
 
             # Call notify.sh
-            res = subprocess.run([args.notify, summary, email], input=body_text)
+            res = subprocess.run([notify, summary, email], input=body_text)
             if res.returncode != 0:
                 backup.log('E', f"failed to send notification")
                 errors += 1