Original bug title:
Make limited information from API:Filearchive available to everyone
When it comes to identifying copyright violations and [[WP:Sock puppetry]], it is essentially helpful if you can check whether a file has been previously uploaded without uploading the file into the stash yourself.
title and size, filterable by sha1
( fasha1=HEXHASH&faprop=title|size )
What about privacy?
Not an issue. If you upload to a file to the stash, you are able to obtain this information anyway.