title: Migration versions across multiple directories
body: <p>If I want to organize my migrations in multiple directories (let's say I'm using SQL migrations, and under the "sql" directory I have a "main" directory and then a "special" directory).</p>
  
  <p>So under sql/main I have "V1.1__some_change" etc.</p>
  
  <p>Then I want to put other migrations under sql/special as well. But the migration version numbers have to be distinct across all the directories, e.g., I couldn't put "V1.1__some_other_change" in sql/special as it would cause a conflict. </p>
  
  <p>But it's not that easy to manage a linear version number across many different directories. Is there a good approach to solve this issue?</p>
  
  <p>Hope this question is clear. </p>