CI: be compatible with both Rustup pre-1.28.0 and 1.28.0

[samueltardieu]

rustup show active-toolchain will no longer install the default toolchain starting from Rustup 1.28.0, and rustup toolchain install without extra arguments is not supported in Rustup pre-1.28.0.

The Rustup change and proposed solution is described in https://internals.rust-lang.org/t/seeking-beta-testers-for-rustup-v1-28-0/22060.

changelog: none

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[ehuss]

I think the TOOLCHAIN=$(rustup show active-toolchain | cut -f1 -d' ') line will also need to be updated (the new output includes multiple lines instead of one).

[samueltardieu]

I think the TOOLCHAIN=$(rustup show active-toolchain | cut -f1 -d' ') line will also need to be updated (the new output includes multiple lines instead of one).

Right, I've now limited the output to the first line, which should give equivalent results, thanks.

[samueltardieu]

@flip1995 I added the missing changelog. I'll add an item to my todo list: to check the presence of a changelog line in the PR check, and not wait until the merge, I'll submit a later PR about this.

[flip1995]

I'll add an item to my todo list: to check the presence of a changelog line in the PR check, and not wait until the merge

That would be great!

It should only involve moving this check from the clippy_mq.yaml to the clippy_pr.yaml file IIRC.