# File lib/mongoid/versioning.rb, line 36
    def revise
      previous = previous_revision
      if previous && versioned_attributes_changed?
        versions.build(previous.versioned_attributes).attributes.delete("_id")
        if version_max.present? && versions.length > version_max
          versions.delete(versions.first)
        end
        self.version = (version || 1 ) + 1
      end
    end