[PATCH COGITO] Do not make cross device hard links

cg-clone doesn't work across devices:

cd /tmp # my tmp is on seperate partition
mkdir cg
cd cg
cg-clone /home/snake/cg/
....
`/home/snake/cg/.git/objects/85/eb3d54aeec1d0f4cf3d2de257b8d7e29816147' -> 
`.git/objects/85/eb3d54aeec1d0f4cf3d2de257b8d7e29816147'
cp: cannot create link 
`.git/objects/85/eb3d54aeec1d0f4cf3d2de257b8d7e29816147': Invalid 
cross-device link
-----------

I have decided that problem should be solved by omitting -u flag while 
fetching in cg-pul;:
$fetch -s -d "$uri/objects" ".git/objects" || die "rsync error"

My variant of autodetection is probably very ugly, but it's works for me :)

-- 
Respectfully
Alexey Nezhdanov