subtree woes

Hello,

I'm shifting my projects to use a subtree system, and I'm having some trouble.
Looks like I'm hitting a subtree-merge bug, although I thought they
were all fixed by now.

I'm using cygwin, git 1.7.9 and apenwarr's git-subtrees repo.
I've also tried git 1.7.10.msysgit.1 with apenwarr's git-subtrees.

I've created a repo on github with a test:
https://github.com/paulharris/subtree_test

The procedure is described in the readme, and has the results too.

In short, I set up a superproject, with some subproject/subtrees.
I have a branch that is my subtree, and now I want to merge it,
like so:
git subtree merge -P zlib origin/subtrees/zlib

Instead of merging the subfolder, it clears the super-project and all
I am left with is the zlib project !

thanks!
Paul