revset: make sort() do dumb multi-pass sorting for multiple keys (issue5218) Our invert() function was too clever to not take length into account. I could fix the problem by appending '\xff' as a terminator (opposite to '\0'), but it turned out to be slower than simple multi-pass sorting. New implementation is pretty straightforward, which just calls sort() from the last key. We can do that since Python sort() is guaranteed to be stable. It doesn't sound nice to call sort() multiple times, but actually it is faster. That's probably because we have fewer Python codes in hot loop, and can avoid heavy string and list manipulation. revset #0: sort(0:10000, 'branch') 0) 0.412753 1) 0.393254 revset #1: sort(0:10000, '-branch') 0) 0.455377 1) 0.389191 85% revset #2: sort(0:10000, 'date') 0) 0.408082 1) 0.376332 92% revset #3: sort(0:10000, '-date') 0) 0.406910 1) 0.380498 93% revset #4: sort(0:10000, 'desc branch user date rev') 0) 0.542996 1) 0.486397 89% revset #5: sort(0:10000, '-desc -branch -user -date -rev') 0) 0.965032 1) 0.518426 53%