Retention policy per year

[Massimo-B]

Hi, as far as I understand section RETENTION POLICY from man btrbk.conf, it is currently not possible to define a count per year or per any other period.

For instance, I currently have:
target_preserve 30d 24w 12m 8y
That means 30 days, 24 weeks, 12 months and 8 years are kept. So after 12 months, only 1 snapshot per year is kept. That means I can't define that after 12 months I like to keep 2 snapshots per year.

A proposal how to define such a policy: Additionaly to the current keywords
[<hourly>h] [<daily>d] [<weekly>w] [<monthly>m] [<yearly>y]
add the new keywords
[<perhour>ph] [<perday>pd] [<perweek>pw] [<permonth>pm] [<peryear>py]

For my case the new policy would be:
target_preserve 30d 24w 12m 8y 2py

Please comment and rate this idea...