* Called from the confirmation screen to actually initiate the migration.
*/
@RequirePOST
public void doStart(StaplerRequest req, StaplerResponse rsp, @QueryParameter String username, @QueryParameter String password) throws ServletException, IOException {
Jenkins hudson = Jenkins.getInstance();
hudson.checkPermission(Jenkins.ADMINISTER);
final String datasetName;
ByteArrayOutputStream log = new ByteArrayOutputStream();
StreamTaskListener listener = new StreamTaskListener(log);
try {