Avoid that garbage_collector deletes images that are still in use

[Bonko]

Description

When having the newly introduced garbage_collector enabled, all tags older than the specified time are deleted, regardless if there are any (possible) used tags left.

This results in complete repositories that get deleted when images are not build regularly.

It would be a great help to ensure that tags that are still used are not deleted.
Using the tag parameter does not help here.

Ideas that came to my mind for this:

• check if the tag was still accessed (pulled) during the specified older_than timeframe before deleting
• add an option "keep_latest_x_tags" which lets you specify to always keep the newest X tags

Portus version: 2.4

• Implementation config: improved garbage collector options #2095
• Documentation docs: updated garbage collector new option and behavior #2100

[mssola]

Makes total sense. Thanks for the feedback 👍