yams #174042 [diff] add missing features & fix bogus features [done]

The schema difffeature is only half-done. Let's complete it.

prioritynormal
typeenhancement
done in<not specified>
load1.000
load left0.000
closed by#8dddcb70070a [diff] transform schema-diff feature to help produce more meaningful diffs
patch[diff] transform schema-diff feature to help produce more meaningful diffs [applied]