Jenkinsfile: build only changed files

changesets.groovy

#!groovy
@NonCPS
def getACIChangeSets() {
  def aci = []
  currentBuild.rawBuild.getChangeSets().each { cs ->
    cs.getItems().each { item ->
      item.getAffectedFiles().each { f ->
        if (f.path.endsWith(".yml")) {
          aci << f.path
        }
      }
    }
  }
  return aci
}

def acis = [:]
def aci = { f ->
  def file_name = f
  acis[f] = {
    node ('my-builder'){
      checkout scm
      sh "aci_build ${file_name}"
    }
  }
}

def c = getACIChangeSets()
for (i = 0; i < c.size(); i++) {
  aci c.get(i)
}                                                                               

stage name: "Build ACI", concurrency: 8
parallel acis

Noways, it's even possible without whitelisting access to the raw build, see https://support.cloudbees.com/hc/en-us/articles/217630098-How-to-access-Changelogs-in-a-Pipeline-Job-