l.s.g.LiveFSFilePruner(BulkPruner) : class documentation

Part of lp.scripts.garbo View In Hierarchy

A BulkPruner to remove old `LiveFSFile`s.

We remove binary files attached to `LiveFSBuild`s that are more than
`LiveFS.keep_binary_files_interval` old and that are not set as base
images for a `DistroArchSeries`; these files are very large and are only
useful for builds in progress.

DAS base images are excluded because
`DistroArchSeries.setChrootFromBuild` takes a `LiveFSBuild` and we want
to have the option of reverting to a previous base image shortly after
upgrading to a newer one.

Text files are typically small (<1MiB) and useful for retrospective
analysis, so we preserve those indefinitely.