rust-hg-core: move from `ouroboros` to `self_cell`
`ouroboros` has a fundamental soundness problem that, while not applicable
today, could become applicable given new compiler optimizations.¹
`self_cell` is a crate that accomplishes a lot of the same things that
`ouroboros` did while remaining sound (that is, unless a new soundness issue
is discovered) by not assuming as much about the memory layout of the program.
`self_cell` has been scrutinized heavily in the past few months by very
competent people, some from the compiler team and has shown no weaknesses
for a while, with a 1.0 stable release coming out a couple months ago.
Our internal API is exactly the same, this is just an implementation detail.
To reiterate, no actual soundness issue was found with our use of `ouroboros`,
but there might be evolutions of `rustc` (or even a future separate compiler)
that could generate unsound code.
[1] https://github.com/joshua-maros/ouroboros/issues/88
====================================
Testing head checking code: Case D-1
====================================
Mercurial checks for the introduction of new heads on push. Evolution comes
into play to detect if existing branches on the server are being replaced by
some of the new one we push.
This case is part of a series of tests checking this behavior.
Category D: remote head is "obs-affected" locally, but result is not part of the push
TestCase 1: remote head is rewritten, but successors is not part of the push
.. old-state:
..
.. * 1 changeset branch
..
.. new-state:
..
.. * 1 changeset branch succeeding the old branch
.. * 1 new unrelated branch
..
.. expected-result:
..
.. * pushing only the unrelated branch: denied
..
.. graph-summary:
..
.. A ø⇠○ A'
.. |/
.. | ◔ B
.. |/
.. ●
$ . $TESTDIR/testlib/push-checkheads-util.sh
Test setup
----------
$ mkdir D1
$ cd D1
$ setuprepos
creating basic server and client repo
updating to branch default
2 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ cd client
$ hg up 0
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ mkcommit A1
created new head
$ hg debugobsolete `getid "desc(A0)" ` `getid "desc(A1)"`
1 new obsolescence markers
obsoleted 1 changesets
$ hg up 0
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ mkcommit B0
created new head
$ hg log -G --hidden
@ 74ff5441d343 (draft): B0
|
| o f6082bc4ffef (draft): A1
|/
| x 8aaa48160adc (draft): A0
|/
o 1e4be0697311 (public): root
Actual testing
--------------
$ hg push -r 'desc(B0)'
pushing to $TESTTMP/D1/server
searching for changes
abort: push creates new remote head 74ff5441d343
(merge or see 'hg help push' for details about pushing new heads)
[20]
$ cd ../..