Improve debuggability of autogenerated_files.py

Signed-off-by: Hanno Becker <[email protected]>

scripts/autogenerate_files.py

@@ -57,9 +57,15 @@ def update_file(filename, content, dry_run=False):
         with open(filename, "r") as f:
             current_content = f.read()
         if current_content != content:
+            filename_new = f"{filename}.new"
             print(
-                f"Autogenerated file {filename} needs updating. Have you called scripts/autogenerated.py?"
+                f"Autogenerated file {filename} needs updating. Have you called scripts/autogenerated.py?",
+                file=sys.stderr,
             )
+            print(f"Writing new version to {filename_new}", file=sys.stderr)
+            with open(filename_new, "w") as f:
+                f.write(content)
+            subprocess.run(["diff", filename, filename_new])
             exit(1)