revset: categorize wdir() as very fast function The cost of wdir() should be identical to or cheaper than _intlist().

revset: make children() not look at p2 if null (issue5439) Unlike p1 = null, p2 = null denotes the revision has only one parent, which shouldn't be considered a child of the null revision. This was spotted while fixing the issue4682 and rediscovered as issue5439.

setup: pass named argument to setup_zstd The next release from upstream adds another named argument to this function. Specify arguments by name so there is no ambiguity about which argument is being passed.