[llvm] [CI][format] Explicitly pass extensions to git-clang-format (PR #95794)

[Louis Dionne via llvm-commits]

https://github.com/ldionne created https://github.com/llvm/llvm-project/pull/95794

This ensures that the CI script controls which file extensions are considered instead of letting git-clang-format apply its own filtering rules. In particular, this properly handles libc++ extension-less headers which were passed to git-clang-format, but then dropped by that tool as having an unrecognized extension.

>From 44bbb0e3718302f61064948efb401988cb9df615 Mon Sep 17 00:00:00 2001
From: Louis Dionne <ldionne.2 at gmail.com>
Date: Mon, 17 Jun 2024 10:08:38 -0400
Subject: [PATCH] [CI][format] Explicitly pass extensions to git-clang-format

This ensures that the CI script controls which file extensions are
considered instead of letting git-clang-format apply its own filtering
rules. In particular, this properly handles libc++ extension-less headers
which were passed to git-clang-format, but then dropped by that tool
as having an unrecognized extension.
---
 llvm/utils/git/code-format-helper.py | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/llvm/utils/git/code-format-helper.py b/llvm/utils/git/code-format-helper.py
index f1207026704e8..48f44fd4431c0 100755
--- a/llvm/utils/git/code-format-helper.py
+++ b/llvm/utils/git/code-format-helper.py
@@ -216,6 +216,15 @@ def format_run(self, changed_files: List[str], args: FormatArgs) -> Optional[str
             cf_cmd.append(args.start_rev)
             cf_cmd.append(args.end_rev)
 
+        # Gather the extension of all modified files and pass them explicitly to git-clang-format.
+        # This prevents git-clang-format from applying its own filtering rules on top of ours.
+        extensions = set()
+        for file in cpp_files:
+            _, ext = os.path.splitext(file)
+            extensions.add(ext.strip(".")) # Exclude periods since git-clang-format takes extensions without them
+        cf_cmd.append("--extensions")
+        cf_cmd.append("'{}'".format(",".join(extensions)))
+
         cf_cmd.append("--")
         cf_cmd += cpp_files