What is the status of bzr shallow branches?

[david ingamells]

The mailing list seems to have gone very quiet on the subject of shallow 
branches. I was hoping to see it released in 1.4, but I can find no sign 
of it in the 1.4rc1. What is the status of this feature?

When it does arrive I hope it will be the branch equivalent of  a 
checkout --lightweight; a branch with it's own (shallow) repository but 
detached from the parent repository as far as actions such as commit and 
merge are concerned.