[clang] [C++20] [Modules] Introduce thin BMI (PR #71622)

[Ben Boeckel via cfe-commits]

mathstuf wrote:

> Sorry for that. But I think it may not be a big deal since people who still want to take an eye this can made it by clicking two times simply.

The timing is also unfortunate as some may have already gone on vacation and will miss updates until they return. Anyways, what's done is done.

> The more the comments are, the more confused readers get. Generally a cleaner PR is not suggested since it lost the context.

It is unfortunate that Github sucks so much at rendering discussions (e.g., GItLab's threads that can be resolved makes it easy to collapse down finished things), There is the "mark as off-topic" strategy that I've seen used before, but that is also conflating the desire to hide things with spam control. In the future I would suggest mentioning those who have participated in the prior PR directly so that there's no gap in email/notification coverage.

https://github.com/llvm/llvm-project/pull/71622