title: Is there an `update migration` (ala South) option for django.db.migrations?
body: <p>In South there was a nice command:</p>
  
  <p><code>schemamigration frontend --auto --update
  </code></p>
  
  <p>Which would take the most recent (unapplied) migration and update it to match whatever change was in the model.  It was really handy during dev.</p>
  
  <p>Does the new django migrations module that was introduced in 1.7 have an option like that?  Looking at the docs I suspect not: <a href="https://docs.djangoproject.com/en/1.7/ref/django-admin/#django-admin-makemigrations" rel="nofollow">https://docs.djangoproject.com/en/1.7/ref/django-admin/#django-admin-makemigrations</a></p>