revset: added isascending and isdescending methods to smartset classes
This methods state if the class is sorted in an ascending or descending order
We need this to implement methods based on order on smartset classes in order
to be able to create new objects with a given order.
We cannot just rely on a simple boolean since unordered set are neither
ascending nor descending.
Test issue2761
$ hg init
$ touch to-be-deleted
$ hg add
adding to-be-deleted
$ hg ci -m first
$ echo a > to-be-deleted
$ hg ci -m second
$ rm to-be-deleted
$ hg diff -r 0
Same issue, different code path
$ hg up -C
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ touch does-not-exist-in-1
$ hg add
adding does-not-exist-in-1
$ hg ci -m third
$ rm does-not-exist-in-1
$ hg diff -r 1