[alembic] equivalent to `makemigrations --check`

[Chris Withers]

Hi,

I got a bounce-back from attempting to email the old alembic google group, so trying here instead!

Does Alembic have an equivalent to django's "makemigrations --check"?

This is a thing you can use in CI on pull requests to ensure no changes
have been made to the model that are not reflected in migrations.

I guess this boils down to "is the current db state plus any outstanding
migrations equal to the model in this checkout"...

cheers,

Chris