This will be used as a step in removing reachable() in a future diff.
Doing it now because bryano is in the process of rewriting ancestors in
C. This depends on bryano's patch to replace *revs with revs in the
declaration of revlog.ancestors.
Accepting a variable number of arguments as the old API did is
deeply ugly, particularly as it means the API can't be extended
with new arguments. Partly as a result, we have at least three
different implementations of the same ancestors algorithm (!?).
Most callers were forced to call ancestors(*somelist), adding to
both inefficiency and ugliness.
This patch adds two methods to revlog:
- ancestors: given a list of revisions returns their ancestors
- descendants: given a list of revisions return their descendants