Extension:CategoryWatch

The CategoryWatch extension extends watchlist functionality to include notification about membership changes of watched categories.

Echo support was recently added to this extension as well as support for modern extension loading.

Rationale
A feature that's missing from the MediaWiki Watchlist functionality is that if you watch a category page, you will only be notified when the content of the category page text changes. You won't be notified when pages are added to or removed from that category though which is probably the main information you were wanting when deciding to watch a category page.

This extension was developed primarily to be used in conjunction with the RecordAdmin extension (which is obsolete), but it's also very useful by itself. When used with these extensions, it's used to allow roles to be notified when work items have changed state and been moved into a category they're responsible for.

Configuration
The global variable called $wgCategoryWatchNotifyEditor can be set to true which will allow the user who re-categorises an article to also receive the notification message if it is a category they are watching. This is useful so that the editor has an audit trail of all membership changes to categories they're watching.

A new global variable called $wgCategoryWatchUseAutoCat can be set to true which causes users to automatically be watching a category of the name Category:Automatically watched by  (set it the categorywatch-autocat message). For example, if you were logged in to the wiki as User:Foo, then you would automatically be notified of any changes to articles in Category:Automatically watched by Foo.

Another related global called $wgCategoryWatchUseAutoCatRealName was added on July 15th 2010 which modifies the automatically watched category function to work with real name's instead of username's. If this was set to true for the example discussed in the previous paragraph, the category name might be something like Category:Automatically watched by Henry McFoo.