ancestor.missingancestors: calculate start point after filtering revsvisit Any revs that are filtered out are also in basesvisit, which means they wouldn't be returned in the missing list anyway. There's no need to explore such revs or their ancestors. The 'if not revsvisit' check moves down because we can't call max() on an empty set.

ancestor.missingancestors: don't discard from basesvisit We only actually care about whether revsvisit is empty, so we can let basesvisit grow to arbitrary size. It turns out that this actually helps performance. For a large repo with hundreds of thousands of commits, hg perfrevset 'only(0, tip)' (basically the worst case, involving a full DAG traversal) goes from 1.63 seconds to 1.50. hg perfrevset 'only(tip, 0)' remains unchanged at 1.98 seconds.