It allowed replacement of the PageArchive object, which is so horrific
that I'm going to have nightmares for a while after seeing that code.
A new hook, PageUndelete, was added to give users something to migrate
to that is also used by API requests etc, and for symmetry with
DeletePage.
This change needs to be in 1.37, since the capability of replacing
PageArchive will be removed in 1.38 by the addition of the UndeletePage
service. Note that in 1.37, errors from the status will not be used
since PageArchive::undeleteAsUser returns false in case of errors.
The only usage of this hook in WMF production (ext:Newsletter) is fixed
in a dependent patch. A non-WMF usage in ext:Video is not fixed since
that one does replace PageArchive and I'd rather not mess with that.
SpecialUndelete has two other similar hooks that pass a PageArchive by
reference, but in those places PageArchive is used as a lookup (not an
undeletion command), so they're not affected by the ongoing undeletion
work, and we cannot deprecate them since we'd have to provide
replacements first. I've left some comments anyway.
Bug: T290021
Change-Id: If434c7ff9de92482f84d535baae5139c18081174
eedd8a7774