I have a stack of 13 draft patches on top of a public revision b37b6c015168. I pull from upstream, get a bunch of new changesets, the top one is 1adf382a3e65. The first 8 patches in my stack have landed upstream, so I'm hoping to discard those in favor of their public versions. I rebase my stack on top of the new patch:
% hg rebase -d 1adf382a3e65
(I was updated to the tip of my patch stack.) I do a bunch of manual merging, then when the rebase is complete it says
12 new orphan changesets