Sangeeta NB [off-list ref] writes:

Yes, I agree. We need to make some changes in `git rebase` to make it
work from the subdirectory, but that doesn't mean that we should
completely restrict it from running in the subdirectory, and the same
follows for `git bisect`.

You actually don't have to make "bisect" work from the subdirectory.

You instead can detect the case where your $cwd may be made to
disappear, and allow "git bisect" to continue if you are certain
that you are not in the funny situation.  You need to protect the
user from funny situation by refusing to run from a subdirectory
only when needed.

Besides, as Phillip mentioned, there is a big difference between two
commands, isn't it?

"git rebase" would ask for help to the end-user by returning the
control when anything goes wrong (e.g. it may not be able to replay
a commit while the user is sitting in a directory that has already
gone), but "git bisect run" would just interpret any failure, not
just the ones that are caused by genuine test failure but caused by
$cwd going away, as "we saw a bad revision".  It would cause a lot
of wasted cycles, instead of immediately stopping when there is
trouble.  So the first thing that has to happen if we want to allow
"bisect" to run from anywhere is to teach it to detect when the $cwd
went away, and stop to give control back to the user to deal with
the situation (it might be the matter of "cd /path/to/top" at that
point), instead of blindly continuing.  Only after that is in place,
we can safely allow it to start from a subdirectory.

Thanks.