[clang-tools-extra] [clang-tidy] introduce a unused local non trival variable check (PR #76101)

[Piotr Zegar via cfe-commits]

https://github.com/PiotrZSL requested changes to this pull request.

Minor tuning needed, some changes to documentation, options, default configuration.


https://github.com/llvm/llvm-project/pull/76101