Upload files still exist even when we delete all posts using it, and wasting disk space if there's too many files.I think a command line API should be given at least.
There is a report that shows abandoned files. You can delete them manually. A bit of a pain, but there is little other way to be sure that something isn't needed.
@BDHarrington7 Correct. At current, we do not associate uploaded files with a particular user, although there should be plugin hooks in place that will allow third-party plugins to maintain this association (for expiry purposes, etc).
