Hey everyone,

Sorry for participating in the discussions so late. I thought I need
to have enough knowledge first before participating.

If a step in the rebase sequence makes a directory disappear (or
turns a directory into a file), and the command given by -x is in
the directory (it is immaterial if it is given as relative or full
pathname from the command line), hopefully the step of the rebase
sequence that would lose the directory would error out, in order to
prevent an untracked but not ignored file from getting clobbered.

Even before speculating such an "advanced" mode of operation, do we
know that rebasing a history that makes a directory disappear and
reappear work?

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`.

What I think that we should allow `git bisect` from any subdirectory.
We can add some warnings in case if there's some error while bisecting
from a subdirectory in the same way by which we handle the errors in
`git rebase` and let the user decide whether he still wants to
continue bisecting from that subdirectory or abort it and run it from
the top-level directory.