Comment 1 for bug 419241

So I tracked the segfault down into code that is passing a node with parents=None to _push_node which isn't supposed to be possible. (The code in _push_node assumes that it can check the parents list as a tuple, etc.)

I've got a quick way to reproduce this, so that part of this bug should be fixed soon.

I don't have a great idea (yet) as to how to handle the issues with stacking and find_ancestry. I think the interface gives back missing keys, so it might not be too bad.

(How to handle it with bzr+ssh repos that don't have stacking set up... I really don't know)