My pom structure is: pom.xml has a parent: parent-pom.xml. Both have a <resources> section to include files.
The (child) pom.xml is executed directly and has the effect of only copying the child's resources. Commenting out this resource section, results in the parent's resources being copied. I believe this is a bug due to no aggregation, but merely shadowing. There's no mention of intended behaviour in the plugin docs. X.
