revset: return early when revs is empty By introducing an early return in _revancestors() when revs is empty, we make it so inputrev is never None, which simplifies the subsequent code.

revset: rename 'revsnode' to 'inputrev' in ancestors We usually use 'node' for variable containing 20 bytes hash. There is nothing nodish in this variable, so we rename it to "inputrev" as it old the next entry of the iteration.

revset: make generatorset.__nonzero__ lazy The 'for r in self:' call could trigger full consumption of the generator while we only need a single value. We also fast path if a single value got already computed. See inline comment for more details. This provide massive speedup for lazy operation using boolean testing. max(::tip) e5b507efb36e) wall 0.055609 comb 0.060000 user 0.060000 sys 0.000000 (best of 100) after change) wall 0.000109 comb 0.000000 user 0.000000 sys 0.000000 (best of 19146)