Deletes old builds leaving only the ones given by MAX_TO_KEEP variable

deleteOldBuildsJob.groovy

import java.util.ArrayList

def MAX_TO_KEEP = 10
def JOB_NAME = "job_name_here"

def hi = hudson.model.Hudson.instance
def item = hi.getItemByFullName(JOB_NAME)
def jobs = item.getAllJobs()

Iterator<?> iterator = jobs.iterator()

while (iterator.hasNext()) {
  def job = iterator.next()
  def recent = job.builds.limit(MAX_TO_KEEP)
  for (build in job.builds) {
      if (!recent.contains(build)) {
         println "Preparing to delete: " + build
 		    build.delete()
      }
  }
}