Split from T16862: Allow global renaming of global users.
- A@global (composed of A@commonswiki and A@metawiki both attached),
- B@global (composed of B@wikidatawiki and B@metawiki both attached)
- C@global (composed only of C@mediawikiwiki).
Current situation (since T16862 was fixed) is that B and C can't be renamed to A. This means that all the users forcefully renamed for T37707: Complete unification of all accounts to SUL (if on more than one wiki) will have to request rename on Meta and only RenameUser will help.
However, this means that all such accounts will be unattached, and this is less than ideal, beside being a pain for everyone involved. All such users will be in the case B, because requesting rename creates a local account on Meta, and A will probably have to confirm too.
What we need is:
- C can be renamed to A: C@global is deleted, the local account is attached to A@global.
- B can be renamed to A: the wikidatawiki account is attached to A@global, while B@metawiki is left behind and B@global stays.