private Optional<ConfigChangeAction> compareStartupCommand(Service currentService, Service nextService) {
        String currentCommand = currentService.getStartupCommand().orElse("");
        String nextCommand = nextService.getStartupCommand().orElse("");

        if (Objects.equals(currentCommand, nextCommand)) return Optional.empty();

        String message = String.format("Startup command for '%s' has changed.\nNew command: %s\nCurrent command: %s",
                                       currentService.getServiceName(), nextCommand, currentCommand);
        return Optional.of(new VespaRestartAction(ClusterSpec.Id.from(currentService.getConfigId()),
                                                  message,
                                                  currentService.getServiceInfo()));
    }
Compares the startup command for the services in the next model with the ones in the current model.
If the startup command has changes, a change entry is created and reported back.

@author bjorncs
config-model/src/main/java/com/yahoo/vespa/model/application/validation/change/StartupCommandChangeValidator.java