evolve: fix the dirstate after setting parents with dirty wdir (issue5930)
Before this patch, during an interrupted evolve it can be confused
about copies. This patch fix the dirstate when parents are changed
using dirstate.setparents() with a dirty wdir.
Changes in test file reflect the fixed behaviour.
#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