As suggested in the docker description I put my repository in /opt/jboss/wildfly/mygit and mapped this directory as a volume
I was able to create a new repository and to import some processes.
When I remove my container (docker rm id) and run it again (docker run ...) I get the following error:
FATAL] Non-resolvable parent POM: Failure to transfer <<repository_name>>:pom:1.0 from http://<<ip>>:8080/jbpm-console/maven2/ was cached in the local repository, resolution will not be reattempted until the update interval of guvnor-m2-repo has elapsed or updates are forced. Original error: Could not transfer artifact <<repository_name>>:pom:1.0 from/to guvnor-m2-repo (http://<<ip>>:8080/jbpm-console/maven2/): Unauthorized (401) @ line 5, column 11