Steps to reproduce:

1. Pick a font available as a classic tarball
2. Select download

Expected behavior:

3. You end up with font_name.tar.gz or font_name.tgz

Actual behavior:

3. You end up with file_name.gz

Problems:

While it's fine to name files using whatever convention you like as UNIX does not have the concept of extensions, this makes it very hard to package fonts for distributions. If download locations contain proper extensions, we can just point our building tools to the correct URL and let them unpack the files. With partial extensions we need to fetch, rename manually and upload to a different site then point the tools to that new URL.

I think the simplest solution would be to only allow raw previews (jpg, png) files (and gzip them) and tarballs (tar+gzip) instead of allowing any file type to be uploaded.