debugcommands: use a revset instead of dagutil...
debugcommands: use a revset instead of dagutil
All this code was doing was finding the nodes that are heads
from the ancestors of an input set. This can easily be expressed
with a revset without having to go through dagutil.
This was the last use of ancestorset() outside of dagutil itself.
Differential Revision:
https://phab.mercurial-scm.org/D4308