Support @quarkusbot retest command

[gastaldi]

It would be nice if we could retrigger the build by commenting something like @quarkusbot retest. Eg. In PRs which updates a dependency that is not in Central yet

This would be useful in conjunction with #23

[glefloch]

I was looking at this one but I can't find a simple way to react to mentions. I'm not even sure we can mention an app. I don't know how dependabot works.. @gsmet have you some hints?

[gsmet]

I think you will have to listen to IssueComment. Note that it's a bit of a pain because you have to check if it's a PR (you have a method for that) and then get the associated pull request and from there you should be able to make progress.

I would do something with a pattern such as ^@(?:quarkus-?)?bot\s+([a-z _\-]+)\s+ and make it case insensitive.

And then have a map of commands.

I would also ignore the comments added by the bot itself but we can add that later as you will need the ability to inject GHMyself and I haven't worked on this yet.

[gsmet]

Ah and better check the pattern before getting the pull request itself, that will avoid one API call.

[glefloch]

Thanks I was missing the part on pull request comment which are issue comments. I will go your way :)