A list of policy options for 'restic forget --prune', to automatically prune old snapshots. See https://restic.readthedocs.io/en/latest/060_forget.html#removing-snapshots-according-to-a-policy for a full list of options.
Note: The 'forget' command is run after the 'backup' command, so keep that in mind when constructing the --keep-* options.
This option is only supported on linux.