feat: Add script to run clang-tidy on changes only

Related to #344

scripts/run_clang_tidy.py

@@ -0,0 +1,43 @@
+#!/bin/env python
+
+# SPDX-FileCopyrightText: Copyright (C) 2025 swift Project Community / Contributors
+# SPDX-License-Identifier: GPL-3.0-or-later OR LicenseRef-swift-pilot-client-1
+
+"""This script runs clang-tidy only on files that have changed compared to the latest origin/main branch."""
+
+import argparse
+
+import utils
+import os
+import subprocess
+
+def run_clang_tidy(build_path: str):
+    src_path = utils.get_swift_source_path()
+    os.chdir(src_path)
+
+    result = subprocess.run(
+        ['git', 'diff', '--name-only', 'origin/main...HEAD'],
+        check=True,
+        stdout=subprocess.PIPE,
+        text=True
+    )
+
+    files = [line for line in result.stdout.splitlines() if (line.endswith('.cpp') or line.endswith('.h')) and not line.startswith('tests')]
+    nproc = os.cpu_count()
+    subprocess.run([
+        'xargs',
+        '-P', str(nproc),
+        '-n', '1',
+        '-r',
+        'clang-tidy',
+        '-p', build_path,
+        '--warnings-as-errors', '*'
+    ], input='\n'.join(files), text=True, check=True)
+
+
+if __name__ == '__main__':
+    parser = argparse.ArgumentParser(prog="swift clang-tidy helper")
+    parser.add_argument("--build-path", required=True, help='Path to build folder')
+    args = parser.parse_args()
+
+    run_clang_tidy(args.build_path)