Just a follow-up to the discussion in https://github.com/jenkinsci/docker-traceability-plugin/pull/18

Here are more details about the HPI and shade Maven plugins incompatibility : http://echelog.com/logs/browse/jenkins/1427839200

Arnaud has already discussed with integer who reported the issue and asked for some help to fix it but for now I did found the time to do it. Here is the feedback he gave regarding the issue :

The issue is that it ignores any package phase bindings and packages jars with hardcoded jar archiver. Jenkins has many issues because of classloader and it will be very convenient to have ability to execute shad-plugin directly from hpi packaging. If packaging is jar, then maven-jar-plugin executes fine maven-shade-plugin. So my idea was to remove hardcoded jar archiver from hpi plugin and give it to maven-jar. https://github.com/jenkinsci/maven-hpi-plugin/blob/ded54b3ac24035ebacda64a0900c3dea5e3de852/src/main/java/org/jenkinsci/maven/plugins/hpi/HpiMojo.java#L122-L131