tests/test-ancestor.py.out

remotefilelog: reduce probability of race-condition in remotefilelog tests

ca1014ad3de4 introduced a new parameter `ensurestart` to speed up
remotefilelog background processes start. Unfortunately it seems to have
increased the possibility of race-conditions in remotefilelog tests testing
those background processes.

With `ensurestart=False`, it seems that it's more probable to enter in a race
condition with `debugwaitonprefetch` and `debugwaitonrepack` in remotefilelog
background tests. Our CI seems to have a high probability of triggering this
race condition so make it configurable to ensure tests are stable.

Differential Revision: https://phab.mercurial-scm.org/D6772

% removeancestorsfrom(), example 1
remaining (sorted): [5, 6, 8, 9]
% removeancestorsfrom(), example 2
remaining (sorted): [11, 12, 13, 14]
% removeancestorsfrom(), example 3
remaining (sorted): [3, 5]
% missingancestors(), example 1
return [3, 7, 11]
% missingancestors(), example 2
return [5, 10]
% missingancestors(), example 3
return [3, 6, 9, 11]
% removeancestorsfrom(), bigger graph
Ok
% lazy ancestor set for [], stoprev = 0, inclusive = False
membership: []
iteration:  []
% lazy ancestor set for [11, 13], stoprev = 0, inclusive = False
membership: [7, 8, 3, 4, 1, 0]
iteration:  [8, 7, 4, 3, 2, 1, 0]
% lazy ancestor set for [1, 3], stoprev = 0, inclusive = False
membership: [1, 0]
iteration:  [1, 0]
% lazy ancestor set for [11, 13], stoprev = 0, inclusive = True
membership: [11, 13, 7, 8, 3, 4, 1, 0]
iteration:  [13, 11, 8, 7, 4, 3, 2, 1, 0]
% lazy ancestor set for [11, 13], stoprev = 6, inclusive = False
membership: [7, 8]
iteration:  [8, 7]
% lazy ancestor set for [11, 13], stoprev = 6, inclusive = True
membership: [11, 13, 7, 8]
iteration:  [13, 11, 8, 7]
% lazy ancestor set for [11, 13], stoprev = 11, inclusive = True
membership: [11, 13]
iteration:  [13, 11]
% lazy ancestor set for [11, 13], stoprev = 12, inclusive = True
membership: [13]
iteration:  [13]
% lazy ancestor set for [10, 1], stoprev = 0, inclusive = True
membership: [2, 10, 4, 5, 0, 1]
iteration:  [10, 5, 4, 2, 1, 0]