tests/test-race

merge: introduce tool.check parameter

tool.check is a list of check options, and can be used in place of
tool.checkchanged and tool.checkconflicts:

Equivalences:
tool.checkchanged = yes
tool.checkconflicts = no
tool.check = changed

tool.checkchanged = no
tool.checkconflicts = yes
tool.check = conflicts

tool.checkchanged = yes
tool.checkconflicts = yes
tool.check = changed, conflicts

Add _toollist() wrapper for ui.configlist() to implement this consistently.

checkchanged and checkconflicts are still supported, but check is
preferred for implementing new check options.

#!/bin/sh

mkdir t
cd t
hg init
echo a > a
hg add a
hg commit -m test

# do we ever miss a sub-second change?
for i in 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20; do
    hg co -qC 0
    echo b > a
    hg st
done