[llvm] code-format: Improve the code-format-helper to be able to run as a git hook (PR #73957)

[Louis Dionne via llvm-commits]

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@@ -128,29 +150,47 @@ def filter_changed_files(self, changed_files: list[str]) -> list[str]:
                 filtered_files.append(path)
         return filtered_files
 
-    def format_run(
-        self, changed_files: list[str], args: argparse.Namespace
-    ) -> str | None:
+    @property
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ldionne wrote:

Not attached to this line, because I can't find where that happens: When I run the hook successfully (i.e. I make a properly-formatted commit), it prints `clang-format did not modify any files`. That seems a bit spurious -- perhaps we don't want to print anything when it succeeds?

https://github.com/llvm/llvm-project/pull/73957