ISPs can't see filenames through TLS. This option is useless in a
codebase that forces HTTPS, and only confuses users.

I swear one of these days I'll just do a search and replace all of them

Value added to source field contains the site name and a random string.
This change prevents uploaders from using self-generated torrent files
unless they also add the source value themselves. This value is provided
to them on the upload page, but is still more inconvenient than before.

Note that this password hashing change will cause an incompatibility
with a fraction of hashes made before this change. A migration is
necessary.