hg.py: add islocal() and defaultdest() functions, refactor islocal tells if a repo or url is local. defaultdest returns default path for clone if explicit path not given. clone can now take repo or url as source

#!/bin/sh

mkdir t
cd t
hg init
echo a > a
hg add a
hg commit -m "test" -d "1000000 0"
hg verify
hg parents
hg status
hg rollback
hg verify
hg parents
hg status