Exit if reapplying last migration generates schema changes

.gitea/workflows/tests.yml

@@ -35,6 +35,7 @@ jobs:
           done
       - run: |
           bundle exec rake db:schema:load db:migrate:status db:migrate:redo
+          git diff --exit-code db/schema.rb
           bundle exec rspec
         env:
           RAILS_ENV: test