How to: Recreate and reprocess your files stored on fog

Recording this here for others with the same issue.

Let's say you're storing your carrierwave files on S3 or some other cloud storage provider through fog.

Let's say you've made some changes to your versions and/or processing of these files and you wish to re-process everything.

With file storage this is simple but with fog it's a bit less straight-forward. The magic incantation is:

YourModel.all.each do |ym| 
  ym.your_uploader.cache_stored_file! 
  ym.your_uploader.retrieve_from_cache!(ym.your_uploader.cache_name) 
  ym.your_uploader.recreate_versions! 
  ym.save! 
end

The trick here is that when you call retrieve_from_cache!, your_uploader.file becomes a CarrierWave::SanitizedFile where it was previously a CarrierWave::Storage::Fog::File.

Good luck!