title: How to run continuous integration in parallel across multiple Pull Requests?
body: <p>I am testing use of Jenkins with <a href="https://wiki.jenkins-ci.org/display/JENKINS/GitHub+pull+request+builder+plugin" rel="nofollow">Github pull request builder plugin</a> I have successfully set up a toy project on Github and dev installation of Jenkins so that raising a PR, or pushing changes to a PR branch triggers a build. Mostly this works as required - a few things don't match preferred workflow, but the freedom from having to write and maintain our own plugin is a big deal.</p>
  
  <p>I have one potential showstopper. The plugin queues up all pushes in all PRs it sees, and only ever seems to run a single job at a time, even with spare executors available. In the real world project, we may have 10 active PRs, each may get a few pushed updates in a day in response to QC comments, and the full CI run takes > 30 mins. However, we do have enough build executors provisioned to run multiple jobs at the same time.</p>
  
  <p>I cannot see any way to configure the PR request builder to process multiple jobs at once on the same trigger, but I may be missing something basic elsewhere in Jenkins. Is there a way to do this, without needing to customise the plugin?</p>
  
  <p>I have installed Jenkins ver. 1.649 on a new Ubuntu 14.04 server (on a VirtualBox guest) and followed the README in the <a href="https://github.com/jenkinsci/ghprb-plugin/blob/master/README.md" rel="nofollow">ghprb plugin</a> (currently version 1.30.5), including setting up a jenkins "bot" account on Github as a collaborator to run all the integration API calls to Github.</p>
  
  <p>I was wondering what the behaviour would be if I cloned the job (create new item and "Copy existing item"), and may try that next, but I expect that will result in the <em>same</em> job being run multiple times for no benefit as opposed to interacting smartly with other jobs polling the same pool of PRs.</p>