The yaml tags !override and !exclude seem to do exactly the same, except that !override requires some properties/subnodes and throws some cryptic (not even the filename, which caused the error, is logged) error message, if there are no properties/subnodes.

I suggest, that !exclude is removed and !override is adapted, so it doesn't require any properties/subnodes to be set and therefore behaves exactly like jcr's extends:override, which developers are used to.

e.g. the following should work

default.yaml

someNode: 
  someProp: true
someOtherNode:
  someOtherProp: true

adapted.yaml

!extend:/default.yaml
someOtherNode: !override

expected result of adapted.yaml:

someNode:
  someProp: true