tests/test-issue1089

setup: use sys.executable to call hg

Executing ".\hg" does not work on Windows, but we can instead ask
Python to execute hg.

#!/bin/sh

hg init a
cd a
mkdir a
echo a > a/b
hg ci -Am m
hg rm a
hg ci -m m a

mkdir a b
echo a > a/b
hg ci -Am m
hg rm a
cd b
# relative delete
hg ci -m m ../a