[Jenkins Seed Multibranch Jobs] initialize multibranch projects with the first sha #Jenkins

initialize_multibranch.groovy

import org.boozallen.plugins.jte.config.*;
import org.jenkinsci.plugins.workflow.multibranch.WorkflowMultiBranchProject;
import org.jenkinsci.plugins.github_branch_source.GitHubSCMSource;
import hudson.plugins.git.GitSCM;
import hudson.plugins.git.BranchSpec; 
import hudson.plugins.git.UserRemoteConfig;
import jenkins.branch.BranchSource;
import org.jenkinsci.plugins.github_branch_source.BranchDiscoveryTrait;
import org.jenkinsci.plugins.github_branch_source.OriginPullRequestDiscoveryTrait;
import jenkins.scm.api.trait.SCMSourceTrait;
import jenkins.scm.impl.trait.WildcardSCMHeadFilterTrait;
import org.boozallen.plugins.jte.config.TemplateConfigFolderProperty;
import org.boozallen.plugins.jte.config.GovernanceTier;
import org.boozallen.plugins.jte.job.TemplateBranchProjectFactory;
import jenkins.model.Jenkins;
import com.cloudbees.hudson.plugins.folder.*; 
import jenkins.branch.buildstrategies.basic.SkipInitialBuildOnFirstBranchIndexing;
import jenkins.branch.BranchBuildStrategy; 
import com.cloudbees.hudson.plugins.folder.computed.PeriodicFolderTrigger;

String githubCredId = "github" 
String githubOwner = "myGitHubOwner"
Stirng repo = "myGitHubRepositoryName"

/* create GitHub SCM source */
def scm_source = new GitHubSCMSource(owner, repo)
scm_source.setCredentialsId(githubCredId)

/* set configuration */
List<SCMSourceTrait> traits = new ArrayList<>()
traits.add(new BranchDiscoveryTrait(1))
traits.add(new OriginPullRequestDiscoveryTrait(1))
scm_source.setTraits(traits)

/* create branch source from SCM */
def branch_source = new BranchSource(scm_source)

/* use basic-build-strategy plugin to skip triggering the jobs on first index */
List<BranchBuildStrategy> strats = [ new SkipInitialBuildOnFirstBranchIndexing() ]
branch_source.setBuildStrategies(strats)

List<BranchSource> sources = new ArrayList<>()
sources.add(branch_source)

/* create multibranch job */
def multi_branch_job = new WorkflowMultiBranchProject(jenkins, job_name)
multi_branch_job.setSourcesList(sources)

/* sets the Build Recognizer to Jenkins Templating Engine */
multi_branch_job.setProjectFactory(new TemplateBranchProjectFactory())

/* have the job poll the SCM every minute */
PeriodicFolderTrigger trigger = new PeriodicFolderTrigger("1")
multi_branch_job.addTrigger(trigger)

/* add job to jenkins */
jenkins.add(multi_branch_job, multi_branch_job.name)

/*
	the good part: 
	1. trigger first indexing and wait for it to complete.
*/
def future = multi_branch_job.scheduleBuild2(0).getFuture()
while(!future.isDone()){
  sleep(1000)
}

/*
	2. get the revision found during the first indexing
       and set this to be the branch's current SHA so that
       future indexing doesn't trigger unless there's been 
       a change
*/
def factory = multi_branch_job.getProjectFactory()
multi_branch_job.getItems().findAll{ branch -> 
  def revision = factory.getLastSeenRevision(branch)
  factory.setRevisionHash(branch, revision) 
}