MediaWiki::performRequest/SpecialPageFactory::executePath/SpecialPage::run/MovePageForm::execute/Title::newFromText
https://github.com/wikimedia/mediawiki/blob/75c813cc9/includes/specials/SpecialMovepage.php#L66-L78
$target = !is_null( $par ) ? $par : $request->getVal( 'target' ); .. $oldTitleText = $request->getVal( 'wpOldTitle', $target ); $this->oldTitle = Title::newFromText( $oldTitleText );