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.
$ cat >> $HGRCPATH << EOF
> [storage]
> dirstate-v2.slow-path=allow
> [format]
> use-dirstate-v2=no
> EOF
Set up a v1 repo
$ hg init repo
$ cd repo
$ echo a > a
$ touch file-with-somewhat-long-name-to-make-dirstate-v1-bigger-than-v2
$ hg commit -Aqm a
$ hg debugrequires | grep dirstate
[1]
$ ls -1 .hg/dirstate*
.hg/dirstate
Copy v1 dirstate
$ cp .hg/dirstate $TESTTMP/dirstate-v1-backup
Upgrade it to v2
$ hg debugupgraderepo -q --config format.use-dirstate-v2=1 --run | grep -E 'added:|removed:'
added: dirstate-v2
$ hg debugrequires | grep dirstate
dirstate-v2
$ ls -1 .hg/dirstate*
.hg/dirstate
.hg/dirstate.* (glob)
Manually reset to dirstate v1 to simulate an incomplete dirstate-v2 upgrade
$ rm .hg/dirstate*
$ cp $TESTTMP/dirstate-v1-backup .hg/dirstate
There should be no errors, but a v2 dirstate should be written back to disk
$ hg st
$ ls -1 .hg/dirstate*
.hg/dirstate
.hg/dirstate.* (glob)
Corrupt the dirstate to see how the errors show up to the user
$ echo "I ate your data" > .hg/dirstate
$ hg st
abort: working directory state appears damaged! (no-rhg !)
(falling back to dirstate-v1 from v2 also failed) (no-rhg !)
abort: Too little data for dirstate: 16 bytes. (rhg !)
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