Reference:UserMerge

Extension: UserMerge

all extensions

Overview
Description:	Merges several users into one account.
State:	stable	Dependency:	MediaWiki
Developer:	Tim Laqua, Thomas Gries, Siebrand Mazeland	License:	GPL v3 only
Type:	MediaWiki	Category:	Administration
Edition:	BlueSpice free, BlueSpice pro, BlueSpice Farm"BlueSpice Farm" is not in the list (BlueSpice free, BlueSpice free (deactivated), BlueSpice pro, BlueSpice pro (deactivated), BlueSpice farm, BlueSpice farm (deactivated), BlueSpice cloud, BlueSpice cloud (deactivated)) of allowed values for the "BSExtensionInfoEdition" property., BlueSpice Cloud"BlueSpice Cloud" is not in the list (BlueSpice free, BlueSpice free (deactivated), BlueSpice pro, BlueSpice pro (deactivated), BlueSpice farm, BlueSpice farm (deactivated), BlueSpice cloud, BlueSpice cloud (deactivated)) of allowed values for the "BSExtensionInfoEdition" property.	Version:	4.1+
For more info, visit Mediawiki.

UserMerge extension allows wiki users with the usermerge permission (Bureaucrat by default) to merge one Wiki user's account with another Wiki user's account.

The extension allows to

• merge (refer contributions, texts, watchlists, edit count of a first account A to a second account B
• delete the first account A after the merge (option box)

Limitations

• you cannot delete a user A without having merged the user A to B
• you cannot merge your own account (logged-in user) into a different user

Extras

• if you omit the "New User" field, then the extension auto-populates the New User as "Anonymous" (user_id 0), and ask you to confirm a merge to Anonymous. This is used for user deletion: you first empty (merge to user 0) contributions of a user A, and then delete the user A.
• If your version of the extension complains about an empty "New User" field you can fill in  "Anonymous".

For more information please visit MediaWiki.