Strange failure with mv and commit

[Ali Sabil]

> Can also try and reproduce the problem manually like so:
>
> bzr init testbranch
> cd testbranch
> echo test>b
> bzr add b
> bzr mv b a
> bzr commit -m "Actually no, a"
> bzr mv a b
> bzr commit -m "No, really, b"
>
it also fails for me with

aborting commit write group: DuplicateFileId(File id
{b-20090702103256-yoexgc9sairjwwem-1} already exists in inventory as
InventoryFile('b-20090702103256-yoexgc9sairjwwem-1', 'a',
parent_id='TREE_ROOT',
sha1='4e1243bd22c66e76c2ba9eddc1f91394e57f9f83', len=5,
revision=ali.sabil at gmail.com-20090702103312-coa1s8uiqvq27jg1))
bzr: ERROR: File id {b-20090702103256-yoexgc9sairjwwem-1} already
exists in inventory as
InventoryFile('b-20090702103256-yoexgc9sairjwwem-1', 'a',
parent_id='TREE_ROOT',
sha1='4e1243bd22c66e76c2ba9eddc1f91394e57f9f83', len=5,
revision=ali.sabil at gmail.com-20090702103312-coa1s8uiqvq27jg1)