generatorset: explicitly track iteration order
The expected iteration order may be different than the fast iteration order (eg:
ancestors(42) is expected to be iterated upward but is fast/lazy to compute
downward.
So we explicitly track the iteration order and enforce it if the manual
iteration is requested.
Default expected iteration order of a generator set is ascending because I'm
not aware of any descending revset that need a generatorset. The first to find
such descending revset will have the pleasure to make this configurable.
Test update logic when there are renames
Update with local changes across a file rename
$ hg init
$ echo a > a
$ hg add a
$ hg ci -m a
$ hg mv a b
$ hg ci -m rename
$ echo b > b
$ hg ci -m change
$ hg up -q 0
$ echo c > a
$ hg up
merging a and b to b
warning: conflicts during merge.
merging b incomplete! (edit conflicts, then use 'hg resolve --mark')
0 files updated, 0 files merged, 0 files removed, 1 files unresolved
use 'hg resolve' to retry unresolved file merges
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