Handling release notes for language guarantees made in the Reference

[traviscross]

Recently, in the Reference, we merged rust-lang/reference#2264. This is a new language guarantee, and I'd expect we'd want to document that in the release notes in the same spirit as earlier ones such as:

• Document NaN bit patterns guarantees
• Guarantee layout and ABI of Result in some scenarios
• Document maximum allocation size
• Document Rust ABI compatibility between various types

I'm not certain about the process for this with the new tooling when this guarantee is made in the Reference rather than in rust-lang/rust. I've added a relnotes label in https://github.com/rust-lang/reference to use for this, if that helps.

@rust-lang/release: Thoughts?

[Mark-Simulacrum]

I would suggest that whenever the reference is bumped in rust-lang/rust, the PR containing these changes is tagged relnotes and then you can edit the auto-created issue with relevant context. That should ensure it gets picked up by the tooling and milestoned for the right release (once the relnotes PR is merged). Editing the reference by itself doesn't (imo) commit us until that change rides the train to stable after such a submodule bump.

https://forge.rust-lang.org/release/release-notes.html documents the relnotes process in more detail.

[traviscross]

Thanks. I worry, in practice, that we'll miss these without tooling support. We reliably bump the submodule pointer for the books ahead of each beta bump (and, between those, at other intervals). But we don't have a system for working backward from this to find everything that should be in the release notes when doing these mechanical bumps.

https://forge.rust-lang.org/release/release-notes.html documents the relnotes process in more detail.

In that document, it notes:

Once labeled, a new issue is automatically filed with title “Tracking issue for release notes of #xxxx: $original pr title”...

Note that this step happens on labeling, not necessarily when the issue/PR is merged/closed.

In the Reference, I'd expect us to add these labels when merging. Then, since we reliably update the submodule pointer ahead of the beta bump, it should be roughly predictable in which release the item will land.

Would it make any sense to extend this create-relnotes-tracking-issue-on-labeling behavior to the Reference repo as well? (I imagine these tracking issues would live in rust-lang/rust.)