Use <kbd>[[Special:ApiHelp/compare|action=compare]]</kbd> instead. Text to diff each revision to. Only diffs a limited number of revisions. Overrides <var>$1diffto</var>. If <var>$1section</var> is set, only that section will be diffed against this text.
MediaWiki:Apihelp-query+revisions+base-param-difftotext/en-gb