> This approach will cause a problem when multi-pack bitmaps are able to > be generated from `git repack`, since the reference tips can change > during the repack. Even though we ignore commits that don't exist in > the MIDX (when doing a scan of the ref tips), it's possible that a > commit in the MIDX reaches something that isn't. > > This can happen when a multi-pack index contains some pack which refers > to loose objects (which by definition aren't included in the multi-pack > index). > > By taking a snapshot of the references before we start repacking, we can > close that race window. I can understand why we want the refs to remain the same both for the MIDX generation and the MIDX bitmap generation (one reason that comes to mind is how we select the commits for which to generate bitmaps), but I don't understand what referring to loose objects has to do with it. I think that using the same set of refs for MIDX generation and bitmap generation is a good enough reason to do this, and we don't need to mention loose objects. The patch itself looks good.
