[llvm] [Code Coverage] Add a tool to check test coverage of a patch (PR #71841)

[Aiden Grossman via llvm-commits]

https://github.com/boomanaiden154 commented:

Quite a few nits, lots of other comments on my initial pass.

This looks like it could be pretty useful. Thanks for putting this together! I'm envisioning this as an on demand job that can be run on a PR with a rich representation reported in a comment (something to be added later) could be a pretty good litmus check for a lot of things.

One question: It seems like this doesn't currently cover cases where only source files or only test files are touched. Just looking at test files might be difficult as there's no way to know what to report. But, looking at just source files I think would be doable (would just require running the whole test suite, not sure how expensive this is) and would be really useful for refactorings and probably other cases.

https://github.com/llvm/llvm-project/pull/71841