def set_revision_meta_attribute(revision, attribute, value)
      case value
      when Symbol
        value = self.send(value)
      when Proc
        value = value.call(self)
      end
      revision.send("#{attribute}=", value)
    end
def set_revision_meta_attribute(revision, attribute, value)
      case value
      when Symbol
        value = self.send(value)
      when Proc
        value = value.call(self)
      end
      revision.send("#{attribute}=", value)
    end
Set an attribute based on a meta argument