It won't result in the third graph on its own as E isn't reachable from D, but it could if you first merged D and E together and then used --update-refs with --

It won't result in the third graph on its own as E isn't reachable from D, but it could if you first merged D and E together and then used --update-refs with --rebase-merges. You could then just discard the merged branch and only take care of D' and E' on their own (and since you don't care about the merged branch, you don't have to care about resolving conflicts while preparing it either).