A very common problem one has if one has enough files stacked up in one place, is whether or not those files have been copied to another system already. Have they already been copied off? To where on the other system were they copied? Sure, you can deduplicate them through various means but that tends to be kind of a sledgehammer thing to do, especially when one of the things with files is a mobile device. You could always upload the files to a provider's cloud¹ storage, like Google Drive or iCloud or something.

But what if you don't …