checkout without touching HEAD

Is there a way to get a 'checkout' of a treeish _directly_ from git to
an empty (or 'no conflicting paths'-guaranteed) directory, without
touching HEAD?

Using `git-archive ... | tar -x` is a waste of time and resources -- I
do want this to be fast for large datasets. I have hacked it a bit by
backing up HEAD, using git checkout with a temporary index, and then
restoring HEAD, which I can do because my script has a big fat lock
around it. But it's very un-gittish to need a big lock around me.

Maybe there's a command I'm missing? Or a zikrit option to checkout I
haven't found?

cheers,


m