HydraWiki is nowadays a part of Wikia, and the majority of their code is FOSS and published on GitLab, and they accept patches (!), which is super cool. Sadly codesearch has only three HydraWiki GitLab repositories indexed -- EmbedVideo, PDFEmbed and Tabber -- as those used to live on the HydraWiki GitHub back when HydraWiki was a Curse project and more closed source than open.

Currently HydraWiki has 71 custom or forked extension repositories (i.e. extensions they've written themselves or extensions forked from their upstream versions for whatever reason(s), as opposed to code that comes straight from WMF gerrit without any modifications), 3 custom skins, the MW repo...it'd be useful to have at least the extensions and skins indexed on codesearch, given that HydraWiki accepts patches and runs on a somewhat recent version of MediaWiki.