Maybe the issue is they think of a PR as an expensive thing. Would be best if they could just do the small thing and make a PR of that from the get-go. If they want to base future changes on the ones they just did, they can just create a new feature branch from right there, and just not create the PR of the second feature until the first is merged, or create it and add a note to the reviewer that it includes the changes of the other PR so they should review that one first. Should they want to add changes to the first feature, they just need to checkout that branch, do the changes, and merge to the second feature branch so they're available there.