smartset: use native set operations as fast paths For set operations like "&" and "-", where we know both basesets have their sets ready, and the first set is sorted, use the native Python set operations as a fast path. Note: "+" is not optimized as that will break the ordering. This leads to noticeable improvements on performance: revset | before | after | delta ---------------------------------------------------------------- draft() & draft() & draft() & draft() | 776 | 477 | -39% draft() + draft() + draft() + draft() | 2849 | 2864 | draft() - draft() + draft() - draft() | 943 | 240 | -75% draft() - draft() - draft() - draft() | 557 | 197 | -64% (time measured in microseconds)