# File lib/chef/knife/cookbook_delete.rb, line 100
      def ask_which_versions_to_delete
        question = "Which version(s) do you want to delete?\n"
        valid_responses = {}
        available_versions.each_with_index do |version, index|
          valid_responses[(index + 1).to_s] = version
          question << "#{index + 1}. #{@cookbook_name} #{version}\n"
        end
        valid_responses[(available_versions.size + 1).to_s] = :all
        question << "#{available_versions.size + 1}. All versions\n\n"
        responses = ask_question(question).split(',').map { |response| response.strip }

        if responses.empty?
          ui.error("No versions specified, exiting")
          exit(1)
        end
        versions = responses.map do |response|
          if version = valid_responses[response]
            version
          else
            ui.error("#{response} is not a valid choice, skipping it")
          end
        end
        versions.compact
      end