code: @VisibleForTesting
    void deployConfig(String filename, DeployProjectConfigurationConfiguration configuration)
        throws AppEngineException {
      Preconditions.checkNotNull(configuration);
      Preconditions.checkNotNull(configuration.getAppEngineDirectory());
  
      Path deployable = configuration.getAppEngineDirectory().resolve(filename);
      Preconditions.checkArgument(
          Files.isRegularFile(deployable), deployable.toString() + " does not exist.");
  
      List<String> arguments = new ArrayList<>();
      arguments.add("app");
      arguments.add("deploy");
      arguments.add(deployable.toAbsolutePath().toString());
      arguments.addAll(GcloudArgs.get("server", configuration.getServer()));
      arguments.addAll(GcloudArgs.get("project", configuration.getProjectId()));
  
      try {
        runner.run(arguments, null);
      } catch (ProcessHandlerException | IOException ex) {
        throw new AppEngineException(ex);
      }
    }
docs: Common configuration deployment function.
  
  @param filename Yaml file that we want to deploy (cron.yaml, dos.yaml, etc)
  @param configuration Deployment configuration