Some extensions provide additional features if other extensions are installed. However, extensions change over time, so that you might need to check which version of an extension is installed. ExtensionRegistry should provide an easy way to check this, as it's a common use case that shouldn't be implemented in parallel many times.
Customize query in gerrit
|mediawiki/core||master||+50 -2||registration: Add ability to check if a specific extension version is loaded|