Jenkins Groovy script to read Git repo branches and list them in an array, can be suited with Active Choice Jenkins Plugin

list-git-branches.groovy

#!/usr/bin/env groovy

/**
 * List all Git branches of a repo.
 * @author thabet.amer@gmail.com
 * @since Jenkins 2.204.1
 * @params String url for Git repo URL, String credentialID, Bool activeChoice if ActiveChoice plugin used, String defaultBranch
 * @return String array of branch names
 *
 * Dependencies:
 * - Jenkins 2.
 * - Jenkins credentials.
 * - Key SSH credentials for the Git repo.
 * - Commands of ssh-agent, ssh-add and git.
 * - Optional: Active Choice Jenkins plugin.
 *
 * Tested on Jenkins Script Console
 *
 * For Jenkins, you need to approve below methods, if sandbox security is enabled:
 * - staticMethod com.cloudbees.plugins.credentials.CredentialsProvider lookupCredentials java.lang.Class hudson.model.ItemGroup
 * - signature : method com.cloudbees.plugins.credentials.common.IdCredentials getId
 * - signature : method com.cloudbees.jenkins.plugins.sshcredentials.SSHUserPrivateKey getPrivateKey
 * - signature : staticMethod org.codehaus.groovy.runtime.DefaultGroovyMethods execute java.util.List
 * - signature : new java.lang.StringBuffer
 * - signature : staticMethod org.codehaus.groovy.runtime.ProcessGroovyMethods consumeProcessOutput java.lang.Process java.lang.Appendable java.lang.Appendable
 */

import com.cloudbees.plugins.credentials.CredentialsProvider;
import com.cloudbees.plugins.credentials.common.StandardUsernamePasswordCredentials;
import jenkins.model.Jenkins

def getAllBranches(url, credentialID, activeChoice = false, defaultBranch = 'master') {
  def jenkinsCredentials = CredentialsProvider.lookupCredentials(
          com.cloudbees.jenkins.plugins.sshcredentials.impl.BasicSSHUserPrivateKey,
          Jenkins.instance
  );
  def key = jenkinsCredentials.findResult { it.id == credentialID ? it.privateKey : null }

  if( !key ) {
    return 'Error: credentials not found'
  }

  Process process = ['ssh-agent','bash','-c', "echo '" + key + "' | ssh-add - 2> /dev/null && git ls-remote -t -h " + url].execute()
  def out = new StringBuilder()
  def err = new StringBuilder()
  process.consumeProcessOutput( out, err )
  process.waitFor()
  if( err.size() > 0 ) return err
  if( out.size() > 0 ) {
      def branches = out.readLines().collect { it.split()[1].replaceAll('refs/heads/', '') }
      if( activeChoice ) {
        def defaultBranchIndex = branches.indexOf(defaultBranch)
        if( defaultBranchIndex >= 0 ) branches.set(defaultBranchIndex, defaultBranch + ':selected')
      }
      return branches
  }
}