code: public void deployCron() throws MojoExecutionException {
      stager.stage();
      try {
        deployMojo
            .getAppEngineFactory()
            .deployment()
            .deployCron(
                configBuilder.buildDeployProjectConfigurationConfiguration(appengineDirectory));
      } catch (AppEngineException ex) {
        throw new MojoExecutionException("Failed to deploy", ex);
      }
    }
docs: Deploy only cron.yaml.