public void publishDesiredRepositoriesUpdates(UpgradeContext upgradeContext) throws AmbariException {
    Cluster cluster = upgradeContext.getCluster();
    ambariEventPublisher.publish(new ClusterComponentsRepoChangedEvent(cluster.getClusterId()));
  }
Updates the various repositories and configurations for services
participating in the upgrade or downgrade. The following actions are
performed in order:
<ul>
<li>The desired repository for every service and component is changed
<li>The {@link UpgradeState} of every component host is moved to either
{@link UpgradeState#IN_PROGRESS} or {@link UpgradeState#NONE}.
<li>In the case of an upgrade, new configurations and service
configurations are created if necessary. In the case of a downgrade, any
configurations created by the upgrade are reverted.
</ul>

@param upgradeContext
         the upgrade context holding all relevent upgrade information (not
         {@code null}).
@throws AmbariException
ambari-server/src/main/java/org/apache/ambari/server/stack/upgrade/orchestrate/UpgradeHelper.java