[PATCH] D55245: [clang-tidy] Add the abseil-duration-subtraction check

[Hyrum Wright via Phabricator via cfe-commits]

hwright added a comment.

Thanks for reviewing, I'll go ahead and commit.

I've also removed the hash specialization, since we moved to `llvm::IndexedMap` instead of `std::unordered_map` inside of `getInverseForScale`.


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  https://reviews.llvm.org/D55245/new/

https://reviews.llvm.org/D55245