    # File lib/chef/knife/cookbook_site_install.rb, line 124
          def parse_name_args!
            if name_args.empty?
              ui.error("Please specify a cookbook to download and install.")
              exit 1
            elsif name_args.size >= 2
              unless name_args.last.match(/^(\d+)(\.\d+){1,2}$/) and name_args.size == 2
                ui.error("Installing multiple cookbooks at once is not supported.")
                exit 1
              end
            end
            name_args.first
          end