add util.samestat function for windows. windows does not have os.path.samestat, and stat().st_ino is always zero, so util.samestat always returns false on windows.

#!/bin/sh

hg init a
echo a > a/a
hg --cwd a ci -A -m a
hg clone a b
echo b > b/b
hg --cwd b ci -A -m b
chmod 100 a/.hg
hg --cwd b push ../a
chmod 700 a/.hg