feat(cli/rustup-mode): add rustup ci subcommand

[rami3l]

Part of #5011.

This first version has implemented a few main subcommands:

• rustup ci env: prints a hardcoded base.env taken from Provide a built-in way for rustup to adapt to a CI environment #5011 (comment).
• rustup ci problem-matcher github: prints a hardcoded problem matcher configuration for GitHub¹.

Footnotes

1. Taken from @r7kamura's solution (https://github.com/r7kamura/rust-problem-matchers/blob/7e46a19e8d2f3a44f97b551aee14a7b3cc18fcd0/.github/matchers.json) since it seems to be the most comprehensive of all. ↩

[rami3l]

As per https://github.com/actions-rust-lang/setup-rust-toolchain/blob/8439c15d249cd2e2a5c80ad3da200c3d8c553ae4/action.yml#L145-L149 this will be a no-op on cargo versions that don't support this flag.

View changes since the review

[rami3l]

@weihanglo Is it safe to always set this flag similarly to #5021 (comment)?

View changes since the review

[weihanglo]

For incremental I think so. Cargo shipped a similar thing recently: rust-lang/cargo#17220

For profile dev debug, Cargo will have a new debug profile and we planned to turn off debug for dev profile:
rust-lang/cargo#17214. So, the direction looks pretty aligned.

For registry protocol, we may want to test if there is any version treating it as a hard error if not recognized. I believe no but worth a double check.

[weihanglo]

probably could test pre-1.61 1.61 to 1.68, and post 1.68

[r7kamura]

Feel free to use my solution for whatever you need👍
It actually came from the issue and PR below, so check 'em out if you're interested:

• Not matching on colorized clippy lints, is this expected? r7kamura/rust-problem-matchers#8
• Make rustc and clippy matcher support colorized output. r7kamura/rust-problem-matchers#11

[rami3l]

@r7kamura Thanks a lot for the extra context! I've made you the co-author for this commit as a sign of appreciation.

[weihanglo]

FWIW, I created this thread for t-cargo to take a look, in case others have some ideas/concerns for the cargo part.

#t-cargo > `rustup ci` environment variables

[rustbot]

This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.