Apart from specific versioning support, our tests should focus on the
behaviour of whatever version they're accompanying, regardless of when
they were written.
Application code should *not* do this.
The purpose of this change is to allow copying fail on the same names.
Migrations change database and they should be treated with caution,
if 2 migrations are named the same it's much better to skip migration
and allow user decide if it should be copied or not.
