changegroup: avoid iterating the whole manifest The old code gathered the list of all files that changed anywhere in history and then gathered changed file nodes by walking the entirety of each manifest to be sent in order to gather changed file nodes. That's going to be unfortunate for narrowhg, and it's already inefficient for medium-to-large repositories. Timings for bundle --all on my hg repo, tested with hgperf: Before: ! wall 23.442445 comb 23.440000 user 23.250000 sys 0.190000 (best of 3) After: ! wall 20.272187 comb 20.270000 user 20.190000 sys 0.080000 (best of 3)