[clang] [clang-repl] adding documentation and information for %commands (PR #150348)

[Aaron Danen via cfe-commits]

https://github.com/aadanen created https://github.com/llvm/llvm-project/pull/150348

so far just added undo to the documentation. We can see about implementing %help or something similar. This will attempt to solve issue #143666 

>From 4e24cb20efa22e364d41026ae40aec470ff786aa Mon Sep 17 00:00:00 2001
From: Aaron Danen <aaron.danen at gmail.com>
Date: Wed, 23 Jul 2025 18:01:14 -0700
Subject: [PATCH] added undo to docs in same format as %quit

---
 clang/docs/ClangRepl.rst | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/clang/docs/ClangRepl.rst b/clang/docs/ClangRepl.rst
index 5399036c123fb..9ef82df28ee43 100644
--- a/clang/docs/ClangRepl.rst
+++ b/clang/docs/ClangRepl.rst
@@ -197,6 +197,13 @@ Comments:
    clang-repl> // Comments in Clang-Repl
    clang-repl> /* Comments in Clang-Repl */
 
+Undo:
+=====
+
+.. code-block:: text
+
+   clang-repl>%undo
+
 
 Closure or Termination:
 =======================