revset: improve _descendants performance Previously revset._descendants would iterate over the entire subset (which is often the entire repo) and test if each rev was in the descendants list. This is really slow on large repos (3+ seconds). Now we iterate over the descendants and test if they're in the subset. This affects advancing and retracting the phase boundary (3.5 seconds down to 0.8 seconds, which is even faster than it was in 2.9). Also affects commands that move the phase boundary (commit and rebase, presumably). The new revsetbenchmark indicates an improvement from 0.2 to 0.12 seconds. So future revset changes should be able to notice regressions. I removed a bad test. It was recently added and tested '1:: and reverse(all())', which has an amibiguous output direction. Previously it printed in reverse order, because we iterated over the subset (the reverse part). Now it prints in normal order because we iterate over the 1:: . Since the revset itself doesn't imply an order, I removed the test.