directaccess: make sure gethashsymbols does not return rev numbers With "hg log -r 1 -r 2 -r 3", gethashsymbols will get the following tree: ('func', ('symbol', '_list'), ('string', '1\x002\x003')) Before this patch, it will return ['1', '2', '3'], which are revision numbers and causes unnecessary (expensive) partialmatch lookups. This patch refacts gethashsymbols a bit, making sure the returning values are always filtered.