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

hg init
python -c 'print "confuse str.splitlines\nembedded\rnewline"' > a
hg ci -Ama -d '1 0'
echo clean diff >> a
hg ci -mb -d '2 0'
hg diff -r0 -r1