Parameters $1 and $2 are not documented in fileimporter-textrevisions and fileimporter-filerevisions.
They can be easily documented by editing the following pages:
- https://translatewiki.net/wiki/MediaWiki:Fileimporter-textrevisions/qqq
- https://translatewiki.net/wiki/MediaWiki:Fileimporter-filerevisions/qqq
Thanks!