Plugin fails with anonymous access and empty password in scm url

According to http://maven.apache.org/scm/cvs.html, one should add a separator between the username and the '@' for anonymous access with an empty password. Currently this fails because the plugin expects exactly 6 tokens in the scm url (pom.repository.connection) for pserver access. This makes it impossible to use the changelog plugin at the same time with other plugins that use the scm library (like jdiff).