To start T74907 off slowly, we should move the Wikidata.org and WikimediaBadges extensions to gerrit.
Neither extension is frequently updated and are rather stable, so this shouldn't interfere with anyone's workflow majorly. Steps:
- Import repositories to gerrit
- Move old github repo to github.com/mediawiki and rename it to what gerrit replicates to github so that future changes get replicated and old issues and pull requests get retained. (Name like https://github.com/wikimedia/mediawiki-extensions-WikimediaBadges .)
- Convert Wikidata build procedure to use the gerrit repositories instead of github
At some time after this ticket is solved we hopefully can deploy these extensions through a normal train process instead of having our own Wikidata build.