There is a ringtone in my iTunes library that I once received through a podcast. I’m no longer interested in that podcast and wanted to dissociate the m4r file from the podcast and then delete the podcast from iTunes. However, I wasn’t able to deselect the podcast attribute in the file’s information window.
AtomicParsley Ringtone.m4r --podcastURL '' --podcastFlag false --podcastGUID ''
After deleting the podcast from iTunes, I imported that modified file, without the podcast itself making a reappearance in the list of podcasts.
This should (hopefully) not be neccessary for m4a files, as the media type for these can be changed through the iTunes GUI.