Provide a way for automated implementations to get reference ID of most recent full backup

[SystemFiles]

This is instrumental in automating backup processes that include differential backups.

Simply put, we need a way to store or otherwise obtain the most recent, related, full-backup in a differential backup implementation such that no user interaction is required.

Brainstorming session will be needed to think of best ways to accomplish this task.

Since restore will likely only ever be done manually (unless someone lets me know otherwise), this functionality need not apply to the restore process.

[SystemFiles]

Maybe could write to an environment variable on the host machine?

[SystemFiles]

Likely just use reference names but a dedicated feature might be nice