[llvm] [GitHub] Add greeting comment to opened PRs from new contributors (PR #72384)

[Kristof Beyls via llvm-commits]

kbeyls wrote:

> What's the difference between FIRST_TIME and FIRST_TIME_CONTRIBUTOR?
> 
> Also a question for @kbeyls - maybe we should note that committing to this repo is a sign that they have accepted the license and our "CLA". Not sure where that's documented right now, but I think it might be good to link to that so people have time to review it before the PR is accepted.

We don't have a CLA, so I'm a bit confused about what you mean by "our CLA"?
If we want to point people to copyright and license information related to their contribution, I guess that https://llvm.org/docs/DeveloperPolicy.html#copyright-license-and-patents might be the best section to point to.

I think I've seen some other projects hosted on github use an auto-commenter like in this PR to point out (and let people tick off that they've understood and agreed with) which license they are contributing their code under.

I think it's probably best to not do this as part of this PR.
Maybe we should aim to get a useful commenter-bot for first-time contributors landed as part of this PR; and then use one or more issues/RFCs on how to further improve the content of the comment? That could list the ideas for e.g. pointing out license/CLA-related information and other stuff.

https://github.com/llvm/llvm-project/pull/72384