retention-days-if: days expression [feat req]

[jelmd]

What would you like to be added?

A new statement like retention-days-if: (or an extension of the retention-days: would be nice, so that one can adjust the retention period on demand.

E.g.

retention-days: 1
retention-days-if: 90 github.event_name == 'push' && github.ref_name == 'main'
retention-days-if: 10 github.event_name == 'pull_request'

Last match wins.

Why is this needed?

Its is needed to keep storage area clean, to not clutter it with outdated copies of not-relevant-anymore stuff. The workaround (tasks duplication an using an if: instead) is not, what a real developer wants: error prone, clutters workflows, makes them hard to read and hard to maintain without any reason.