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

[Jessica Paquette via llvm-commits]

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@@ -425,3 +427,144 @@ EXIT STATUS
 
 :program:`llvm-remarkutil size-diff` returns 0 on success, and a non-zero value
 otherwise.
+
+.. _diff_subcommand:
+
+diff
+~~~~~
+
+.. program:: llvm-remarkutil diff
+
+
+USAGE: :program:`llvm-remarkutil diff` [*options*] <remarka_file>  <remarkb_file>
+
+Summary
+^^^^^^^
+
+:program:`llvm-remarkutil diff` hilights the difference between two versions of `remarks <https://llvm.org/docs/Remarks.html>`_ based on specified properties.
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ornata wrote:

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