How to implement the --tag option of nightwatch within a grunt-based test system?

We run tests from grunt, like so: grunt browsertest

Gruntfile.js would have in it:

grunt.registerTask('browsertest', ['nightwatch:browsertest_osx']);

nightwatch.js would have in it:

module.exports = {
  options: {
          'browsertest_osx': {
              globals: {
                  targetmachine: 'http://localhost:3000',
                  username: 'someuser',
                  password: ''
              },
              'launch_url': 'http://localhost:3000',
              'selenium_port': 4444,
              'selenium_host': 'localhost',
              'src_folders': ['Tests/browsertests'],
              'silent': true,
              'screenshots': {
                  'enabled': false,
                  'path': ''
              },
              'selenium': {
                  'cli_args': {
                      'webdriver.chrome.driver': 'bin/chromedriver_osx'
                  }
              },
              'desiredCapabilities': {
                  'browserName': 'chrome',
                  'javascriptEnabled': true,
                  'acceptSslCerts': true
              }
          },                            
      }
  }

};

Now, this means I will run all test scripts in folder 'Tests/browsertests' (see attribute src_folders in nightwatch.js)...
I've found a remedy to it on SE: NightWatch Tags

However, now I am stuck with how to install this functionality into my existing test system.
Let's say I would like to run different areas of the browser tests, which are in their own scripts:
1-browsingZoneA.js, 2-browsingZoneB.js...

And I would like to control which of the above scripts actually gets run by plugging a '@tags': ['browsingZoneA'] into file '1-browsingZoneA.js'...

So, my question is: how should I now invoke these specific tags?
I don't know which is the best command format, but let's say I choose:
grunt browsertest --areaA
- How do I connect areaA to something like: nightwatch --tag smokeTests? Do I add something in nightwatch.js? Or perhaps a conditional grunt.registerTask() in Gruntfile.js?