phases: avoid N² behavior in `advanceboundary`
We allowed duplicated entries in the deque, which each entry could potentially
insert all its ancestors. So advancing boundary for the full repository would
mean each revision would walk all its ancestors, resulting in O(N²) iteration.
For repository of any decent size, N² is quickly insane.
We introduce a simple set to avoid this and get back to reasonable performance.
$ hg init r1
$ cd r1
$ hg ci --config ui.allowemptycommit=true -m c0
$ hg ci --config ui.allowemptycommit=true -m c1
$ hg ci --config ui.allowemptycommit=true -m c2
$ hg co -q 0
$ hg ci --config ui.allowemptycommit=true -m c3
created new head
$ hg co -q 3
$ hg merge --quiet
$ hg ci --config ui.allowemptycommit=true -m c4
$ hg log -G -T'{desc}'
@ c4
|\
| o c3
| |
o | c2
| |
o | c1
|/
o c0
>>> from mercurial import hg
>>> from mercurial import ui as uimod
>>> repo = hg.repository(uimod.ui())
>>> for anc in repo.changelog.ancestors([4], inclusive=True):
... print(anc)
4
3
2
1
0