Make it a rule that any PR that changes over ... 100 LoC? 150? <some number you're comfortable with> needs to be broken down into smaller, more atomic ones.
If that can't be done, e.g. because it's a very large refactor that can only be published as a unit, get them to walk you through each design and architectural choice.
I don't think a high quality contributor will take issue with that.
Comments
Make it a rule that any PR that changes over ... 100 LoC? 150? <some number you're comfortable with> needs to be broken down into smaller, more atomic ones.
If that can't be done, e.g. because it's a very large refactor that can only be published as a unit, get them to walk you through each design and architectural choice.
I don't think a high quality contributor will take issue with that.