Taylor Blau [off-list ref] writes:

I'm not sure that that's the case: Junio pointed out a while[1] ago that
we'd have to answer the question of "what happens if I'm in a
subdirectory that goes away during some point of the bisection?". I
think that you could probably find an answer to that question, but the
fact that there isn't an obvious one seems to indicate that we're going
down the wrong path.

I agree that it would be nice to run bisect from any directory, but it
may not be as easy as I'd hope.

True.

I would not mind all that much a single "git checkout ancient" that
makes the $cwd go away and confuse the user.  But a bisect session
would jump around versions randomly (eh, logarithmically?) and you'd
end up switching out of a version in a non-existing $cwd to another
version that has the directory (created internally by mkdir(2)), and
I'm fairly certain that your phantom $cwd that is not connected to
any other filesystem entity and the directory that should be at the
same path in the newly checked-out version are different filesystem
entities.  I'd rather not have to think about the interaction
between git and the system after that point.

Thanks.