Main development Git repository on Gerrit: https://gerrit.wikimedia.org/r/#/admin/projects/mediawiki/extensions/CategoryWatch
Here is the Phabricator Diffusion: https://phabricator.wikimedia.org/diffusion/ECWA/
Mirror on GitHub: https://github.com/seanchen/CategoryWatch
MediaWiki extension CategoryWatch, https://www.mediawiki.org/wiki/Extension:CategoryWatch
Initial commit is forked from commit 4ad0f63: https://github.com/OrganicDesign/extensions/tree/4ad0f631438ed16c05edfa08e65e0de00b4b1342/MediaWiki-Legacy/CategoryWatch
3 simple steps to debug an extension.
wfDebugLog('CategoryWatch', 'loading extension...');
# in file LocalSettings.php $wgDebugLogGroups['CategoryWatch'] = '/path/to/log/mw-categorywatch.log';