David Kimura PRO said over 3 years ago on Tracking Changes on Action Text :
  You should be able to have a controller action with the content

version = Version.includes(:item).find(params[:id])
itemable = version.item
itemable.content = version.content
itemable.save

It should take the content of the version and set it to the related content. This of course would then create a new version based on this version.