Problem:
The set of repositories covered by [[https://www.mediawiki.org/wiki/Codesearch|codesearch]] is currently limited and ad-hoc, adding repositories to the list is a manual process. With the [[https://www.mediawiki.org/wiki/Stable_interface_policy|Stable Interface Policy]] mentioning codesearch as a preferred way to assess usage of deprecated code in extensions, it is becoming increasingly important to have a light-weight and transparent way for extension authors to ensure their extension is included in the index. Requiring extensions to be hosted on gerrit does not seem desirable.
Proposal:
On a regular bases (e.g. weekly), generate a list of repositories to index based on extensions listed on mediawiki.org. Specifically, pages in the categories [[https://www.mediawiki.org/wiki/Category:Stable extensions|Stable extensions]] and [[https://www.mediawiki.org/wiki/Category:Beta_status_extensions|Beta status extensions]] should be scanned for the `{{Extension}}` template. The link to the relevant git repository can then be extracted from the template parameters (resp. from templates like `{{GithubDownload}}` or `{{WikimediaDownload}}`).
This would provide a transparent and lightweight way to get one's extension included in the index, and thus considered in the deprecation process. Similarly, this would make it trivial to remove unmaintained extensions from the index.
NOTE: this is not presently intended to be an RFC, but it may become one of that appears necessary or useful.