revset: make parents() O(number of parents) Strip executes a revset like this: max(parents(_intlist('1234\x001235')) - _intlist('1234\x001235')) Previously the parents() revset would do 'subset & parents' which iterates over each item in the subset and checks if it's in parents. subset is usually the entire repo (a spanset) so this takes a while. Reversing the parameters to be 'parents & subset' means the operation becomes O(number of parents) instead of O(size of repo). It also means the result gets evaluated immediately (since parents isn't a lazy set), but I think this is a win in most scenarios. This shaves 0.3 seconds off strip (amend/histedit/rebase/etc) for large repositories. revset #0: parents(20000) 0) obsolete feature not enabled but 54243 markers found! ! wall 0.006256 comb 0.010000 user 0.010000 sys 0.000000 (best of 289) 1) obsolete feature not enabled but 54243 markers found! ! wall 0.000391 comb 0.000000 user 0.000000 sys 0.000000 (best of 4323)