Re: [PATCH v4 00/25] multi-pack reachability bitmaps

On Tue, Aug 24, 2021 at 10:10:12PM -0400, Taylor Blau wrote:

quoted

It's not clear to me that we have a resolution on whether calling "cd ..
&& git multi-pack-index write --object-dir repo.git" is supposed to
work.

My recommendation would be to do the following things, all in a reroll
of this series:

  - Fix the bug by which we would delete a .rev or .bitmap file out of a
    different object store than we were working in (when the caller
    passes `--object-dir`).

  - Disallow running `git multi-pack-index` outside of a Git repository.

  - Restrict `--object-dir` to only work with alternates of the
    repository in the current working directory.

To me, that seems like both the least-surprising behavior, and what
would lend itself to the easiest implementation. I would probably argue
that the existing behavior (where `--object-dir` would work against
arbitrary repositories) is a bug, and shouldn't continue to be
supported.

All of those seem reasonable to me, and are what I would suggest if we
were starting from scratch. My only hesitation is whether people are
using the weird behavior of --object-dir in the wild (e.g., are bup
folks relying on it).

Johannes, is this something you're using _now_, and it works, or
something you hoped to use in the future?

In a sense, "hope to use" does not make you any less disappointed. ;)
But what I'm wondering is whether using --object-dir from outside a repo
entirely is actually something that even works. I.e., would we be
disabling a behavior that was not intended, but does happen to work? Or
are we closing off a possibly buggy and half-working part of the system?

-Peff