Add `delete-redirect` for deleting single-rev redirects during moves

A new user right, `delete-redirect`, is added (not given to anyone
by default). At Special:MovePage, if attempting to move to a single
revision redirect that would otherwise be an invalid target (i.e.
doesn't point to the source page), the user is able to delete the
target.

Deletions are logged as `delete/delete_redir2`, and the move is
then logged normally as `move/move`, mirroring current delete and
move logging.

To allow for separate handling by Special:MovePage,
MovePage::isValidMove now returns a fatal status `redirectexists` if
the target isn't valid but passes Title::isSingleRevRedirect.
Otherwise, `articleexists` is returned (as previously). Other callers
that don't intend to treat single revision redirects differently
should treat `redirectexists` the same as `articleexists`.

Currently, this deletion (like normal delete and move) cannot be
done through the move api. Since the deletion is only valid when
moving a page, unlike for normal deletion, deleting redirects with
this right cannot be done via the delete api either.

Bug: T239277
Change-Id: I36c8df0a12d326ae07018046541bd00103936144

1 files changed, 5 insertions, 2 deletions

diff --git a/includes/MovePage.php b/includes/MovePage.php
index 5540aadbb9cd..c99ae72fe98c 100644
--- a/includes/MovePage.php
+++ b/includes/MovePage.php
@@ -222,8 +222,11 @@ class MovePage {
 		} elseif ( $this->newTitle->getArticleID() && !$this->isValidMoveTarget() ) {
 			// The move is allowed only if (1) the target doesn't exist, or (2) the target is a
 			// redirect to the source, and has no history (so we can undo bad moves right after
-			// they're done).
-			$status->fatal( 'articleexists', $this->newTitle->getPrefixedText() );
+			// they're done). If the target is a single revision redirect to a different page,
+			// it can be deleted with just `delete-redirect` rights (i.e. without needing
+			// `delete`) - see T239277
+			$fatal = $this->newTitle->isSingleRevRedirect() ? 'redirectexists' : 'articleexists';
+			$status->fatal( $fatal, $this->newTitle->getPrefixedText() );
 		}
 
 		// @todo If the old title is invalid, maybe we should check if it somehow exists in the