[llvm] Introduce llvmremark util diff command (PR #85007)

[Jessica Paquette via llvm-commits]

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@@ -0,0 +1,298 @@
+//===- RemarkDiff.h -------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// Generic tool to diff remarks based on properties
+//
+//===----------------------------------------------------------------------===//
+
+#include "RemarkUtilHelpers.h"
+#include "RemarkUtilRegistry.h"
+#include "llvm/ADT/MapVector.h"
+#include "llvm/ADT/SetVector.h"
+#include "llvm/ADT/SmallSet.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/JSON.h"
+#include "llvm/Support/Regex.h"
+#include "llvm/Support/ScopedPrinter.h"
+
+namespace llvm {
+namespace remarks {
+
+enum ReportStyleOptions { human_output, json_output };
+/// copy of Argument class using std::string instead of StringRef.
+struct RemarkArgInfo {
+  std::string Key;
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ornata wrote:

`SmallString`?

https://github.com/llvm/llvm-project/pull/85007