push: move obsolescence related message into _pushobsolescence function No good reason to have them in the main fonction.

push: drop now outdated comment This `_pushobsolete` now exist for modularity purpose.

push: feed pushoperation object to _pushobsolete function This will allow the obsolete marker synchronisation to have full information on the ongoing push and pass information to other operation.

push: move obsolescence marker exchange in the exchange module The obsolescence marker exchange code was already extracted during a previous cycle. We are moving the extracted functio in this module. This function will read and write data in the `pushoperation` object and I prefer to have all core function collaborating through this object in the same place. This changeset is pure code movement only. Code change for direct consumption of the `pushoperation` object will come later.

push: feed pushoperation object to _pushbookmark function This will able the bookmark synchronisation to have full information on the ongoing push and pass information to other operation.

merge with stable

revset: added operations to duck type baseset Added more operations which are not lazy but only used so far to duck type baseset. Their implementations will be changed in future patches.

revset: added basic operations to lazyset Added methods __add__, __sub__ and __and__ to duck type more methods in baseset