rebase: support multiple roots for rebaseset We have all the necessary mechanism to rebase a set with multiple roots, we only needed a proper handling of this case we preparing and concluding the rebase. This changeset des that. Rebase set with multiple root allows some awesome usage of rebase like: - rebase all your draft on lastest upstream hg rebase --dest @ --rev 'draft()' - exclusion of specific changeset during rebase hg rebase --rev '42:: - author(Babar)' - rebase a set of revision were multiple roots are later merged hg rebase --rev '(18+42)::'