tests/test-help

fix broken environment save/restore when a hook runs.
move "run commend with different env/cwd" code out to function in util.
new function is called esystem.

#!/bin/sh

hg
hg -q
hg help
hg -q help
hg add -h
hg add --skjdfks
hg help diff
hg help status
hg -q help status
hg help foo
hg skjdfks

exit 0