Hook to warn in unexpected size change

[thiswillbeyourgithub]

Hi!

I noticed recently that I had wrongly added a very large mount folder in a dir backup by restic. Thankfully I had a systemd script using ntfy to warn me of unexpected disk usage. A few terabytes later I noticed the issue!

So it got me thinking: backrest already has all the tooling to add such a feature:

• add a textbox for "Warn if size change larger than X%"
• add a hook to notify the user

In my case, the hook would have triggered bevause the backup trippled in size.

Ideally the % could also be negative, to notify of unexpectedly large pruning.

Thanks for making backrest!