# File lib/bundler/ruby_version.rb, line 44
    def diff(other)
      if engine != other.engine && @input_engine
        [ :engine, engine, other.engine ]
      elsif version != other.version
        [ :version, version, other.version ]
      elsif engine_version != other.engine_version && @input_engine
        [ :engine_version, engine_version, other.engine_version ]
      else
        nil
      end
    end