revset: document wdir() as an experimental function Let's resurrect the docstring since our help module can detect the EXPERIMENTAL tag and display it only if -v is specified. This patch updates the test added by 015c0d1087a3 since wdir() is now documented.

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.