MediaWiki:Apihelp-query+revisions+base-param-difftotext
Text to diff each revision to. Only diffs a limited number of revisions. Overrides $1diffto. If $1section is set, only that section will be diffed against this text.
Text to diff each revision to. Only diffs a limited number of revisions. Overrides $1diffto. If $1section is set, only that section will be diffed against this text.