This gem can be used for either running a Jenkins server, or for plugin development.
It contains the war file for Jenkins and must be run with JRuby (at least 1.6 according to this).
Current version : 1.602.
To use it include it in your Gemfile :
gem 'jenkins-war', git: 'https://github.com/n-rodriguez/jenkins-war.git'
jenkins-war is released under the MIT License.