Use transactional DDL in postgres to prevent ever leaving a dirty flag

[couling]

I don't see anything documented so I hope I'm not missing something obvious.

When our migrations fail for any reason we end up with something like:

Dirty database version 4. Fix and force version.

But Postgres supports transactional DDL. All changes that happen inside transactional DDL are rolled back with the transaction. So, where migrations are executed in a transaction, there should never be any reason to mark it as dirty.

So what would be really neat would be for migrate to have an option with Postgres DBs to take control of the migration's transaction control such that it knows never to mark anything as dirty. Either the migration script runs successfully and it commits, or it is unsuccessful and it rollsback.