stack: introduce and explicite command to display the stack
If is worth testing having the feature lives outside 'hg topic --list'. The
'stack' name is sub optimal because the conflict with 'status'. using "hg st"
would still work as 'st' is hard coded, but this mean 'hg stack' has no short
version.
#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 'set:**.py or grep("^!#.*python")' 2>/dev/null \
> | xargs pyflakes 2>/dev/null