Permalinks destroyed by "unpublish"

[kylewm]

Unpublishing a post, i.e. resaving it as a draft, is (oddly) more destructive than just deleting it because it overwrites the permalink path with the drafts/hash path. And re-publishing it will update the day/time to right now and update the permalink accordingly, so that it's very difficult to ever get it back to its original permalink.

This is probably the desired behavior if you accidentally clicked "Publish" 5 minutes ago, and want a little more time to edit. But if you Unpublish an older post, it could be pretty bad and I'm not totally sure how to fix it. Perhaps draft_path should be a separate DB field.