GMaven uses SLF4J and uses the Gossip provider to allow for simple and flexible configuration of logging output.
When running in Apache Maven 3.0.x without any SLF4J customizations, additional GMaven logging can be enabled by setting the gmaven.logging property on the mvn command-line.
To enable DEBUG logging:
mvn -Dgmaven.logging=DEBUG
To enable TRACE logging:
mvn -Dgmaven.logging=TRACE
Apache Maven 3.1.x provides SLF4J bindings slf4j-simple by default and that binding implementation must be configured to enable more verbose logging details.
To enable logging configuration as described for Apache Maven 3.0+ the 3.1+ distribution needs to be augmented to replace the default SLF4J binding with Gossip.