with: support grandfather-father-son backup rotation scheme in addition to fixed intervals

[markstos]

It would nice to support a more complex backup retention policy, like " keep backups for the last 8 days, 2 weeks, and 1 per month for the last 12 months".

The logic you need is already in the grandfatherson Python module, it just needs to be integrated have the related options exposed to users.

Note I opened an issue with the grandfatherson with a suggestion to make it safer.