>I think we would have to create a new repo and make the PR against the new repo instead.
Why create a new repo? The current is just fine. For instance, I migrated Apache JMeter from SVN to Git, and extra git repositories were not needed. See https://issues.apache.org/jira/browse/INFRA-18499?focusedCommentId=16855765&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#comment-16855765 Vladimir
