revert: add a fullreposet class Every revset evaluation starts from `subset = spanset(repo)` and a lot of revset predicates build a `spansetrepo` for their internal needs. `spanset` is a generic class that can handle any situation. As a result a lot of operation between spanset result in an `orderedlazyset`, a safe object but suboptimal in may situation. So we introduce a `fullreposet` class where some of the operation will be overwritten to produce more interesting results.