index missing

[Stefan Monnier]

I do a daily `bup get` to mirror my backups off-site and it always gives
me (numerous) warnings of the form:

warning: index pack-acf2770998d1077615741e6c9e6e0bf239a4b65b.idx missing
used by midx-b2d613b6feb3efd2161dd82fd7622074c5e82bdb.midx

[ Where the hexadecimal part changes. ]

IIUC those warnings aren't too serious, but I'd still like to understand
where they come from. The things that puzzle me are:
- I can't find any of the mentioned `pack-*` files anywhere.
- I can't find any of the mentioned `midx-*` files anywhere.
- While the `pack-*` names in the warnings recur from one day to the
next, the `midx-*` names are different everytime.
- `bup midx --check objects/pack/midx-*` tells me everything is fine; in
both repositories.

I don't even know if this warning refer to files on the source or the
destination repository.

This is using Debian's `bup-0.33`. What are those warnings telling me?


Stefan