benbalter/WP-Document-Revisions-Code-Cookbook — pull request #3 by pmtarantino (2013-08-21 18:39:56+00:00)
Title: Use get_extension() with attachment file, not original post

I tried to use this plugin but it didn't work. I noticed get_extension works against attached files, not the original post. So I write this little fix (which gets the attachment, and then apply get_extension). It seems to work now.