thoughtbot/paperclip — pull request #1017 by ddonahue99 (2012-09-14 17:39:36+00:00)
Title: Add support for blacklisting content_types

Paperclip currently has support for validating content types using a whitelist approach, e.g.:

```ruby
validates_attachment :image, :content_type => { :content_type => "image/jpg" }
```

This branch adds support for blacklisting content types, as follows:

```ruby
validates_attachment :image, :content_type => { :not => "application/zip" }
```

It works the exact same way as the whitelist but just does the opposite check. You can send in a string, array, or regex.