# File lib/bundler/source/git.rb, line 153
      def install(spec)
        debug = nil
        if requires_checkout? && !@copied
          debug = "  * Checking out revision: #{ref}"
          git_proxy.copy_to(install_path, submodules)
          serialize_gemspecs_in(install_path)
          @copied = true
        end
        generate_bin(spec)
        ["Using #{spec.name} (#{spec.version}) from #{to_s}", nil, debug]
      end