pick: register pickstate as an unfinished state
This way pickstate file will indicate that unfinished pick command needs to be
dealt with (--continue or --abort) before modifying the repo. Otherwise it
would be e.g. possible to commit during an interrupted pick and that's not
expected.
#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