title: How would you create a 'manual' django migration?
body: <p>I've discovered that I can set defaults for columns on a postgres database in a django project using <code>migrations.RunSQL('some sql')</code>.</p>
  
  <p>I'm currently doing this by adding a column, makemigrations, then removing the column, makemigrations, and then manually modifying the migration file that is produced. </p>
  
  <p>I tried copying an old migration file and then removing the old code so just the new sql could be run and got some strange errors.</p>
  
  <pre><code>CommandError: Conflicting migrations detected; multiple leaf nodes in the migration graph: (0067_auto_20180509_2327, 0068_auto_20180514_0707 in csmu).
  To fix them run python manage.py makemigrations --merge
  </code></pre>
  
  <p>How would you create a 'manual' django migration?</p>