ci(deps): detect add-only vendored changes (#13765)

.github/workflows/dependencies/updater.py

@@ -392,13 +392,15 @@ class Git:
         Returns `False` if the repo is dirty.
         """
         try:
-            CommandRunner.run_or_fail(
-                ["git", "diff", "--exit-code"], stage="CheckRepoClean"
+            result = CommandRunner.run_or_fail(
+                ["git", "status", "--porcelain", "--untracked-files=normal"],
+                stage="CheckRepoClean",
             )
-            return True
         except CommandRunner.Exception:
             return False
 
+        return result.stdout.strip() == b""
+
     @staticmethod
     def add_and_commit(scope: str, version: str) -> bool:
         """