Re: [BUG REPORT] Git does not correctly replay bisect log

[Christian Couder <christian.couder@gmail.com>]

On Thu, Dec 6, 2018 at 6:30 PM Lukáš Krejčí <lskrejci@gmail.com> wrote:
>
> I am talking about `git bisect replay`. The shell script, as far as I
> can see, only updates the references (ref/bisect/*) and never checks if
> the revisions marked as 'good' are ancestors of the 'bad' one.
> Therefore, $GIT_DIR/BISECT_ANCESTORS_OK file is never created.

Indeed `git bisect replay` first only updates the references
(ref/bisect/*) according to all the "git bisect {good,bad}"
instructions it finds in the log it is passed. After doing that
though, before exiting, it calls `bisect_auto_next` which calls
`bisect_next` which calls `git bisect--helper --next-all` which checks
the merge bases.

I think it is a bug.

`git bisect replay` is right to only update the references
(ref/bisect/*) and not to compute and checkout the best commit to test
at each step except at the end, but it should probably just create the
$GIT_DIR/BISECT_ANCESTORS_OK file if more than one bisection step has
been performed (because the merge bases are checked as part of the
first bisection step only).

> The first time the ancestors are checked is in the helper (`git-bisect-
> -help --next-all`) that has only limited information from refs/bisect*.

`git-bisect--helper --next-all` knows how to get refs/bisect*
information, otherwise it couldn't decide which is the next best
commit to test.

Thanks for your help in debugging this,
Christian.