# File lib/bundler/fetcher.rb, line 167
    def user_agent
      @user_agent ||= begin
        ruby = Bundler::RubyVersion.system

        agent = String.new("bundler/#{Bundler::VERSION}")
        agent << " rubygems/#{Gem::VERSION}"
        agent << " ruby/#{ruby.versions_string(ruby.versions)}"
        agent << " (#{ruby.host})"
        agent << " command/#{ARGV.first}"

        if ruby.engine != "ruby"
          # engine_version raises on unknown engines
          engine_version = begin
                             ruby.engine_versions
                           rescue RuntimeError
                             "???"
                           end
          agent << " #{ruby.engine}/#{ruby.versions_string(engine_version)}"
        end

        agent << " options/#{Bundler.settings.all.join(",")}"

        agent << " ci/#{cis.join(",")}" if cis.any?

        # add a random ID so we can consolidate runs server-side
        agent << " " << SecureRandom.hex(8)

        # add any user agent strings set in the config
        extra_ua = Bundler.settings[:user_agent]
        agent << " " << extra_ua if extra_ua

        agent
      end
    end