Manual:CreateAndPromote.php/en

Details
createAndPromote.php is a maintenance script that creates a new user or modifies an existing user. For the corresponding user, the script can then grant additional rights (e.g. sysop, bureaucrat or bot rights) and change the user's password.

Since the script can be used not only to create new users, but also on existing users to promote them, and also to create a user without promoting them, the name  is somewhat misleading.

Usage
This creates a new user called "WikiSysop", sets the password and adds the user to the bureaucrat group, the sysop group and to the custom developer group.