[clang] [clang-format] Add DiagHandler for getStyle function (PR #91317)

[Owen Pan via cfe-commits]

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@@ -3945,20 +3945,23 @@ const char *DefaultFallbackStyle = "LLVM";
 
 llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>>
 loadAndParseConfigFile(StringRef ConfigFile, llvm::vfs::FileSystem *FS,
-                       FormatStyle *Style, bool AllowUnknownOptions) {
+                       FormatStyle *Style, bool AllowUnknownOptions,
+                       llvm::SourceMgr::DiagHandlerTy DiagHandler = nullptr) {
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owenca wrote:

It seems we don't need the default `nullptr`.

https://github.com/llvm/llvm-project/pull/91317