Rollup merge of #89929 - yuvaldolev:handle-submodule-checkout-more-gr…

…acefully, r=Mark-Simulacrum

Handling submodule update failures more gracefully from x.py

Addresses #80498

Handling the case where x.py can't check out the right commit of a submodule, because the submodule has local edits that would be overwritten by the checkout, more gracefully.
The error is printed in detail, with some hints on how to revert the local changes to the submodule.

src/bootstrap/bootstrap.py

@@ -1026,7 +1026,15 @@ def update_submodule(self, module, checked_out, recorded_submodules):
         if self.git_version >= distutils.version.LooseVersion("2.11.0"):
             update_args.append("--progress")
         update_args.append(module)
-        run(update_args, cwd=self.rust_root, verbose=self.verbose, exception=True)
+        try:
+            run(update_args, cwd=self.rust_root, verbose=self.verbose, exception=True)
+        except RuntimeError:
+            print("Failed updating submodule. This is probably due to uncommitted local changes.")
+            print('Either stash the changes by running "git stash" within the submodule\'s')
+            print('directory, reset them by running "git reset --hard", or commit them.')
+            print("To reset all submodules' changes run", end=" ")
+            print('"git submodule foreach --recursive git reset --hard".')
+            raise SystemExit(1)
 
         run(["git", "reset", "-q", "--hard"],
             cwd=module_path, verbose=self.verbose)