CI

Stream: std4

[Scott Morrison]

If @Mario Carneiro or @Joe Hendrix could take a look at https://github.com/leanprover/std4/pull/350, this would be very helpful to me.

We already have an automated nightly-testing branch on Std (just like on Mathlib), and this adds something we've already added on Mathlib: whenever we get successful CI on the nightly-testing branch, we create/update the nightly-testing-YYYY-MM-DD branch for the relevant nightly release.

This ensures that nightly-testing-YYYY-MM-DD, when it exists, should always be a "good" version of Std that compiles with the given nightly. Having this invariant available makes it much saner to create lean-pr-testing-NNNN branches that actually work...

[Mario Carneiro]

@Scott Morrison I am 100% okay with you approving and merging commits regarding the CI process on your own

[Scott Morrison]

I see you understand the "whoever touched it last" principle regarding CI. :-)