title: How can I quickly delete many old Pipeline Job builds on a Jenkins server?
body: <p>I have a Jenkins server which has a lot of used space seemingly for no reason at all. After digging around I noticed that old builds were not being discarded for branches that are kept around (<code>master</code> for example). I can fix all the projects by adding a "keep x builds" setting, but I have a lot of projects and I need to clean up the disk straight away.</p>
  
  <p>It's cumbersome and time consuming to manually delete jobs on a Jenkins server, and it is not clear how to proceed if you quickly need to free up some space (except for manually deleting stuff from the hard drive). Deleting stuff from the Jenkins <code>job</code> directory is probably going to leave some cruft in the <code>fingerprints</code> directory too(?) - not a good idea.</p>
  
  <p>How can I quickly clean up a bunch of projects while still leaving say 5 builds per branch in a Pipeline project?</p>