Add detail about how to raise MCP concerns

[apiraino]

During the weekly T-compiler triage meetings we list all MCPs in different stages of progress. Some of them are blocked on concerns not yet resolved. We would like to list these open concerns so that meeting attendees have a glance why an MCP is not seconded or does not move forward.

In order to automate this when creating the meeting agenda it is useful if people respect a standard syntax for that so I can machine parse the issue comments and with a bit of regexps extract the relevant info.

Current message when opening a MCP:

The new version should look like this

Note: the @rustbot syntax here won't trigger anything, It's just a psychological trick to make it look like that a command is executed but in reality it's just to facilitate the machine parsing for me.

Idea mentioned on Zulip.

Documentation update for forge.rust-lang.org: rust-lang/rust-forge#709

Thanks for looking at this patch!

r? @Mark-Simulacrum / @ehuss

[apiraino]

hey gentle ping: could this be useful?

cc: @Mark-Simulacrum / @ehuss

thanks

[Mark-Simulacrum]

I'm not a huge fan of not triggering anything in response to the (fake) command. Are we going to post an error?

@rustbot concern foo bar baz

[Mark-Simulacrum]

I guess no error. I think this is fine but maybe we can say a bit more instead of register - e.g., "formally declare an objection"? It might also be good to have docs we can link to on the actual process here - e.g., should folks clear the concern somehow?

[apiraino]

I agree. It's a hack and not particularly very elegant. But if you think that providing enough context and documentation makes it palatable, I'm happy to do that!

[Mark-Simulacrum]

Yep, I'm happy to merge with some extra context (in the comment or in some doc we link to about the process as a whole).

[apiraino]

ok @Mark-Simulacrum updated the text (hope I got the newlines right), the syntax we will be suggesting reflects the FCP one:

@rustbot concern reason-for-concern

<description of the concern>

and

@rustbot resolve reason-for-concern

Updated the documentation at the forge: rust-lang/rust-forge#709

[apiraino]

@Mark-Simulacrum gentle nudge. thanks.