thoughtbot/paperclip — pull request #1090 by rwz (2012-11-21 15:27:57+00:00)
Title: Added the ability to provide fog file parameters as a lambda.

I was trying to make paperclip add custom S# headers on each new file upload. I also needed these headers to be dynamically calculated.

Basically, this is was I was trying to do:
```ruby
class MyModel < AR::Base
has_attached_file :attachment,
storage: :fog,
fog_credentials: credentials,
fog_file: ->(attachment) {
{ content_disposition: "attachment; filename=#{attachment.instance.generated_name};" }
}

def generated_name
"foobar"
end
end
```

This PR enables paperclip to chew passed lambda as a valid argument for fog_file option.