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

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