Comment 1 for bug 1451627

It's unlikely that we will support auto-conversion like this; it's very common for migration to require some manual adjustments (I've personally had good experiences using http://www.catb.org/~esr/reposurgeon/ to help automate these), and I think the amount of low-level VCS engineering that would be involved in allowing people to use both simultaneously is better spent elsewhere at this point. However, we definitely need to work on making the migration path documented and more obvious.