dirstate: use a presized dict for the dirstate This uses a simple heuristic to avoid expensive resizes. On a real-world repo with around 400,000 files, perfdirstate: before: ! wall 0.155562 comb 0.160000 user 0.150000 sys 0.010000 (best of 64) after: ! wall 0.132638 comb 0.130000 user 0.120000 sys 0.010000 (best of 75) On another real-world repo with around 250,000 files: before: ! wall 0.098459 comb 0.100000 user 0.090000 sys 0.010000 (best of 100) after: ! wall 0.089084 comb 0.090000 user 0.080000 sys 0.010000 (best of 100)