Prevent swap repos appearing in repo list
I kind of think of swap repos as very transient repos. That is, there is not much point in having them keep around for long periods of time. In fact, it would cause problems, because people would try and install apps or update the repo without realising that F-Droid is still expecting to be on the same local network as when the swap took place. The swapee will also need to have their phone enabled and ready to swap, which is even less likely.
Thus, perhaps once we've gotten the index from the repo, we could then forget about the repo. The only problem is, I'm not quite sure how to deal with the apps that were inserted into the database. When should they be removed from the database?