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 -e
umask 027
mkdir test1
cd test1
hg init
touch a b
hg add a b
hg ci -m "added a b" -d "0 0"
cd ..
mkdir test2
cd test2
hg init
hg pull ../test1
hg co
chmod +x a
hg ci -m "chmod +x a" -d "0 0"
cd ../test1
echo 123 >>a
hg ci -m "a updated" -d "0 0"
hg pull ../test2
hg heads
hg history
hg -v co -m
ls -l ../test[12]/a > foo
cut -b 0-10 < foo