Confirm that the extension is a convention mapped object.
Stop class hierarchy to DefaultCopySpec since it's marked @NotExtensible. Then iterated over some groovyc errors which could only be solved by not implementing CopySpec anymore. It's clearly not ideal, but I tried a dozen alternatives and not worked. At least the @Delegate is gone.
Make nexus settings usable as an initscript. Usage: ./gradlew --init-script gradle/nexus.gradle build
Clean up imports to be more explicit, from code reviews.
Removing guava reference
Add message about breaking change for group and description.