Description
For Firefox, we have a script that kind of duplicates the behavior of rustup and that repacks rust for use on Firefox CI. In some cases, we need to pin a specific beta version, but failed to do so, so when 1.24.0-beta.1 replaced 1.23.0-beta.2 today, we ended up picking that, which, incidentally, broke Firefox CI because 1.24.0-beta.1 apparently breaks slog and servo.
Anyways, after some fiddling, it came out that it's possible to get a specific beta version... if you know when it was released.
That is,
$ rustup toolchain install beta-2017-12-08
installs 1.23.0-beta.2. You have to know that 1.23.0-beta.2 was released on that specific day, or scan all dates.
It would be much easier if it were possible to do:
$ rustup toolchain install 1.23.0-beta.2
which could rely on an hypothetical https://static.rust-lang.org/dist/channel-rust-1.23.0-beta.2.toml
file.