[Pulp-list] Question on purging stale rpms

[Partha Aji]

Here is the scenario. 
I synced a repo from some feed which has packages A1, B1. 
Now the feed got updated to packages A2, B1. 
Now when I resync I need my repo to have A2, B1 (exact mirror). The default behaviour in pulp seems to be not touch local repo and hence it ends up having packages A1, A2, and B1. I know there is a way to override this and was trying to figure out the config option.
Looking at https://github.com/pulp/pulp_rpm/blob/master/plugins/pulp_rpm/plugins/importers/yum/purge.py#L18 I notice 2 options "remove-missing" and "retain-old-count". 
1) Do you guys know which option is it.
2) Can I use this option as a sync override, or specify it in an importer config per repo.

Partha