[Idea] - Check for non expired backups

[gliatti]

Hello pgstef,

As I described here I think it would be nice to have a service that checks if there is at least on backup is not really expired. It is still physically presents in the backup directory but pgbackrest info does not have any information about it.

My simple logic would be for backups:

1. Execute pgbackrest info
2. Execute repo-ls
3. Compare the two stdout.

For archived wals, since there is at least a backup we found is orphan, we can only assume there will be non expired archived wals too.

As you told me, it may be a lot of IO on the repo. And I don't have any idea to simply implement it except by:

1. Execute pgbackrest info, and retrieve wal information about first and last wals
2. Checking by a "simple" repo-ls if there are wals prior to the first wal name retrieved by previous command.

Robin from Dalibo,