[llvm] [CAS] Add llvm-cas tools to inspect on-disk LLVMCAS (PR #166481)

[Petr Hosek via llvm-commits]

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@@ -0,0 +1,63 @@
+include "llvm/Option/OptParser.td"
+
+class F<string name> : Flag<["--", "-"], name>;
+
+def grp_action : OptionGroup<"Actions">, HelpText<"llvm-cas actions">;
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petrhosek wrote:

We should be able to support both syntaxes to avoid breaking existing uses and mark the flag-based versions as deprecated so new users are encouraged to use the subcommand syntax. I'm fine doing it in a follow up change if you prefer.

https://github.com/llvm/llvm-project/pull/166481