Document how to use docker-library-bot

[J0WI]

@docker-library-bot seems to update various "official" repos, but this feature is nowhere documented.
Would be great to get some info about that.

Edit: Here is an example.

[tianon]

It's not really anything formal (calling it a "feature" is a bit of a stretch) -- it's a Jenkins user we set up to help us manage all the image repos under https://github.com/docker-library (all of which have an update.sh to bump version numbers and a generate-stackbrew-library.sh to generate the relevant library/REPO file contents).

See https://doi-janky.infosiftr.net/job/update.sh/ for the Jenkins jobs (which are linked from each image repo README.md file) and https://github.com/docker-library/oi-janky-groovy/tree/238af3cbad31c9a27cc9d450c951a68c46d408ba/update.sh for the Groovy scripts. It works well enough for us that several other repos have asked to be included (which can be seen in vars.groovy in that linked repo).

IMO this doesn't really warrant any further documentation since it's not really a "feature" and is simply how we maintain things -- every image maintainer is welcome to do their own thing.

[J0WI]

I think here or here would be a great place to mention that.

[J0WI]

@tianon I tired to automate the Joomla image, but the generate-stackbrew-library.sh is ignored by the bot.

[tianon]

Making PRs to https://github.com/docker-library/official-images isn't something the bot does (it only automates ./update.sh, test building, and committing) -- that's something I do manually.

[wglambert]

Going to close as the question is answered sufficiently