evolve: use repo.setparents() instead of repo.dirstate.setparents()
setparents() was added to localrepository class in 2012, and now we finally
have some differences between calling repo.setparents() vs
repo.dirstate.setparents(): _quick_access_* things, introduced in hg 5.3.
This patch fixes an actual quick-access desync problem where repo[b'.'] would
be different from repo.dirstate.p1(), as demonstrated by
test-evolve-phase-divergence.t when ran on hg 5.3rc0 and later.
Modified _uncommitdirstate() too, because it is used in dirstatedance(), which
sometimes follows repo.setparents() calls.
#require test-repo pyflakes
Copied from Mercurial core (60ee2593a270)
$ cd "`dirname "$TESTDIR"`"
run pyflakes on all tracked files ending in .py or without a file ending
(skipping binary file random-seed)
$ hg locate -I 'set:(**.py or grep("^#!.*python")) - removed()' 2>/dev/null \
> | xargs pyflakes 2>/dev/null