clone: simplifying dest repo creation since creating a repo raises an exception if the repo already exists, there's no need to try to create one. add some test for repo creation when the destination exists

#!/bin/sh

mkdir a
cd a
hg init
echo foo > b
hg add b
hg ci -m "b" -d "1000000 0"

chmod -w .hg

cd ..

hg clone a b

chmod +w a/.hg # let test clean up

cd b
hg verify