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

[David Spickett via cfe-commits]

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@@ -347,7 +348,15 @@ int main(int argc, const char **argv) {
     }
   }
 
+  // if we add more % commands, there should be better architecture than this
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DavidSpickett wrote:

It's fine, point is, it's very clear to the next person that they should think about this.

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