I think my opinion has either changed a bit, or I didn’t express myself clearly, since I made that post.
I’m still not enthusiastic about teaching Rust how to install directly from the rust-ci S3 bucket, but there are other solutions that I think could be fine for rustup.
Contrary to what I said in that issue, I feel pretty good about adding more special-purpose release channels to Rust, e.g. a ‘nightly-fast’ channel. There have been a few other use cases come up recently where the obvious solution to me (as a biased author of rustup) was ‘just publish another release channel’. There seems to be some inertia against this though.
Since I posted my referenced comment on the rustup issue, Rust CI has gained support for publishing try builds to S3 in the same way as the nightly alt builds, and cargobomb has gained custom support (without direct rustup support) for running against them. So that’s no longer a pressing use case for me.
My concerns with teaching rustup about the CI builds are mainly about not having manifests to work with (resulting in degraded and special-cased capabilities), blessing the rust-ci URLs with support, the special naming scheme used by ‘master-alt’ to avoid naming collisions that would need to be hard-coded into rustup, non-discoverability of builds, unsigned toolchains.
Another solution to solve this general problem of pulling builds out of CI and adding them to rustup would be to create a special-purpose tool that downloads those crates by commit and adds them to rustup. It’s pretty easy.