[pbs-devel] [PATCH v2 proxmox-backup 4/4] fix #5331: garbage collection: avoid multiple chunk atime updates

[Christian Ebner]

Forgot to update the commit message on this patch, should be:
```
Reduce the number of atime updates on the same chunk by logically
iterating over image index files, following the datastore iterators
logic. Index files in unexpected locations are still considered, by
generating a list of all images to be found in the datastore and
removing regular index files from that list, leaving unexpected ones
behind.

To reduce the number of atimes updates, keep track of the encountered
chunk digests for consecutive snapshots. Chunks which have been
encountered in the previous snapshot, but are not present in the
current one are removed from the list in order to reduce memory
footprint.
```
Will update this if a further iteration of the patches is requested,
please amend this accordingly otherwise.