tests/test-1102

test-merge-tools: windows fixes

- /bin/cat does not exist, expect 'cat'
- non-interactive mode is not correctly detected in pysh, force it

#!/bin/sh

rm -rf a
hg init a
cd a
echo a > a
hg ci -Am0
hg tag t1 # 1
hg tag --remove t1 # 2

hg co 1
hg tag -r0 t1
hg tags