darcs-style cherry-picking of changes to commit ?

[Simon Michael]

Good evening all.. I'm a happy darcs user, checking out bzr which also 
looks great. Thanks for creating it.

On #bzr I got this help:

sm: does bzr support cherry-picking changes within a file as well as darcs ?
...
taaz: i think sm is asking about the neat feature of darcs asking about 
each individual line grouping diff in a file as you commit.
taaz: so you can just commit partial changes to a file
sm: yes that's what I meant
...
robey: yeah i think the closest bzr behavior is "shelve"
...
robey: but the shelve ui is a bit wonky

and was advised to raise it here also. I wondered if darcs still has 
some algorithmic edge which permits this feature ? Or is it easy enough 
to replicate this feature in bzr by integrating shelve more tightly ?

Best,
-Simon Michael