Accept/decline T-compiler backports from Zulip

[apiraino]

This patch adds a new Zulip command:
@triagebot backport <channel> <action> <PR>

Example:

• @triagebot backport stable accept 123456
• @triagebot backport beta decline 654321

This can be used to post on GitHub a comment like this one when T-compiler accepts/decline to backport a patch that fixes a regression.

Limitations:

• This command assumes that the PR is from rust-lang/rust, I am not aware of other git repos having this workflow. If we want, maybe in the future we can extend to other repos using our custom Zulip linkfiers
• There is no check on the PR number (so if someone mistypes, the comment will go elsewhere 😅 )

Tested on a custom Zulip instance.

TODO:

• update docs on the forge
• Could be interesting a shorter variant of this command (f.e. backport accept or even accept) to be used from #t-compiler/backports (topics contain all necessary info to build the command parameters)

[apiraino]

I guess this patch went under the radar because I didn't request a review

r? triagebot

[Kobzol]

Sounds pretty useful!

View changes since this review

[apiraino]

r? @Kobzol I think it's ready for another round of review (when you have time)

[Kobzol]

Thanks! Left some nits, but otherwise I think that it's fine.

View changes since this review

[Kobzol]

Please just get rid of the merge commit by rebasing, otherwise LGTM :)

View changes since this review

[Kobzol]

I wonder if triagebot reads triagebot commands from its own comments 🤔 I guess we'll see :)

View changes since this review

[apiraino]

I wonder if triagebot reads triagebot commands from its own comments 🤔 I guess we'll see :)

Do you mean if on Zulip calling @triagebot in a comment would trigger a circular @triagebot invocation? I'm not sure about what you mean

[Kobzol]

No, on GitHub. Right now the backport command sends a GitHub comment from triagebot with @rustbot label .... I wonder if triagebot will then read this comment and actually execute the @rustbot label command, even if the GH comment was created by triagebot itself (e.g. bors ignores its own comments).

[apiraino]

ah ok! Yes it will trigger a reaction applying the labels (for GH after all it's a normal comment from a GH user).

Thanks for the review!