obsolete: have _readmarkers return the format version
readmarkers is not returning the version of the format it read from. This will
let callers know about the format and allow them to preserve it.
% ancestors of [] and not of [1]
[]
% ancestors of [] and not of []
[]
% ancestors of [12] and not of []
[0, 1, 2, 4, 6, 7, 9, 12]
% ancestors of [0] and not of [0]
[]
% ancestors of [4, 5, 6] and not of [6, 5, 4]
[]
% ancestors of [-1] and not of [12]
[]
% ancestors of [12] and not of [-1]
[0, 1, 2, 4, 6, 7, 9, 12]
% ancestors of [12] and not of [9]
[12]
% ancestors of [9] and not of [12]
[]
% ancestors of [12, 9] and not of [7]
[6, 9, 12]
% ancestors of [7, 6] and not of [12]
[]
% ancestors of [10] and not of [11, 12]
[5, 10]
% ancestors of [11] and not of [10]
[3, 7, 11]
% ancestors of [11] and not of [10, 12]
[3, 11]
% ancestors of [12] and not of [10]
[6, 7, 9, 12]
% ancestors of [12] and not of [11]
[6, 9, 12]
% ancestors of [10, 11, 12] and not of [13]
[0, 1, 2, 3, 4, 5, 6, 7, 9, 10, 11, 12]
% ancestors of [13] and not of [10, 11, 12]
[8, 13]
% lazy ancestor set for [], stoprev = 0, inclusive = False
[]
% lazy ancestor set for [11, 13], stoprev = 0, inclusive = False
[7, 8, 3, 4, 1, 0]
% lazy ancestor set for [11, 13], stoprev = 0, inclusive = True
[11, 13, 7, 8, 3, 4, 1, 0]
% lazy ancestor set for [11, 13], stoprev = 6, inclusive = False
[7, 8]
% lazy ancestor set for [11, 13], stoprev = 6, inclusive = True
[11, 13, 7, 8]