baseset: fix isascending and isdescending We now have sufficient information to return the proper value there.

baseset: prepare lazy ordering in __iter__ We'll explicitly track the order of the baseset to take advantage of the ascending and descending lists during iteration.

baseset: implement a fastasc and fastdesc Baseset contains already-computed revisions. It is considered "cheap" to do operations on an already-computed set. So we add attributes to hold version of the list in ascending and descending order and use them for `fastasc` and `fastdesc`. Having distinct lists is important to provide correct iteration in all cases. Altering a python list will impact an iterator connected to it. eg: not preserving order at iterator creation time >>> l = [0, 1] >>> i = iter(l) >>> l.reverse() >>> list(i) [1, 0] eg: corrupting in progress iteration >>> l = [0, 1] >>> i = iter(l) >>> i.next() 0 >>> l.reverse() >>> i.next() 0

baseset: stop inheriting from built-in list class The baseset is doing more and more smartset magic and using its list-like property less and less. So we store the list of revisions in an explicit attribute and stop inheriting. This requires reimplementing some basic methods.

strip: stop calling `remove` on smartset The `remove` method is not part of the smartset specification. We use a plain old list comprehension instead.

rebase: transform the smartset to a list before comparing with a list This is highly suboptimal but smartsets are not comparable to lists yet.

merge.update: use `first` instead of direct indexing This makes it compatible with all smartset classes.

qimport: use `first` and `last` instead of direct indexing This makes it compatible with all smartset classes.

rebase: use `last` instead of direct indexing This makes it compatible with all smartset classes.

mq: use `last` instead of direct indexing This makes it compatible with all smartset classes.