[llvm] [CI][format] Explicitly pass extensions to git-clang-format (take 2) (PR #98227)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-mlgo

Author: Louis Dionne (ldionne)

<details>
<summary>Changes</summary>

This is a second attempt to land 7620fe0, which was reverted in 9572388 because it caused formatting not to be enforced for several patches.

---
Full diff: https://github.com/llvm/llvm-project/pull/98227.diff


2 Files Affected:

- (modified) llvm/lib/CodeGen/MLRegAllocEvictAdvisor.cpp (+2) 
- (modified) llvm/utils/git/code-format-helper.py (+11) 


``````````diff
diff --git a/llvm/lib/CodeGen/MLRegAllocEvictAdvisor.cpp b/llvm/lib/CodeGen/MLRegAllocEvictAdvisor.cpp
index 7f90457d720b4..536984e6c9a5a 100644
--- a/llvm/lib/CodeGen/MLRegAllocEvictAdvisor.cpp
+++ b/llvm/lib/CodeGen/MLRegAllocEvictAdvisor.cpp
@@ -10,6 +10,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+// This line should never get through the formatting job clang-format please format this into something that is actually reasonable.
+
 #include "AllocationOrder.h"
 #include "RegAllocEvictionAdvisor.h"
 #include "RegAllocGreedy.h"
diff --git a/llvm/utils/git/code-format-helper.py b/llvm/utils/git/code-format-helper.py
index f1207026704e8..d60d4131bc94b 100755
--- a/llvm/utils/git/code-format-helper.py
+++ b/llvm/utils/git/code-format-helper.py
@@ -216,6 +216,17 @@ 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
 

``````````

</details>


https://github.com/llvm/llvm-project/pull/98227