Change the Generate function to take a SchemaSource instead of a sqldb.Queryable

[the-glu]

Description

This PR change the Generate function to take a SchemaSource instead of a sqldb.Queryable.

Motivation

We're using this library to generate migrations and this option allows us to generate forward and backward migrations, based on the wanted schema and database.

The change allows for better flexibility in Generate and let's us just swap arguments to the function, to generate both migrations at once.

Testing

Tests with the pg-schema-diff-test-runner are passing locally :)

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[bplunkett-stripe]

Thanks for the contribution! I fundamentally agree with what you're trying to do...but maybe think WithReverse is a bit confusing and indicates a bigger flaw with the pg-schema-diff API.

Depending on how much work you want to do here:

With code change

Replace sqldb.Queryable with SchemaSource and change fromDB to fromSchema. This will break backwards compatibility, but I think that's okay(?)

No Code Change

• Use the tempdbfactory to create a database with your target schema DDL and pass that as sqldb.Queryable
• Use the database schema source as the target schema

Let me know if you're interested in the more in-depth code change! I could also try to throw this together!

[the-glu]

Thanks for having a look!

Let me know if you're interested in the more in-depth code change! I could also try to throw this together!

Ok, I can also go with the code change if you're OK with breaking backwards compatibility :)

Any specific hints or direction for the change? I see there is already a DBSchemaSource, so it should be doable without big modifications.

[the-glu]

The PR has been updated with the new code change :)

[bplunkett-stripe]

Looks great! Could you update the code example in the README.md?

[the-glu]

Looks great! Could you update the code example in the README.md?

Yes, it should be fixed now :)

[bplunkett-stripe]

Thanks for updating the README.md! Changes look good to me. Appreciate the contribution!

[the-glu]

Thanks you for the quick review and the approval :)