Rename file name issues

@equivalent Hi,
I trying to rename the duplicated file:

`class Attachment < ActiveRecord::Base`
` mount_uploader :attachment, AttachmentUploader`
` belongs_to :attachmentable, polymorphic: true`
` include CopyCarrierwaveFile`
` def duplicate_file(original)`
` copy_carrierwave_file(original, self, :attachment)`
` self.save!`
` end`
`end`

`class AttachmentUploader < CarrierWave::Uploader::Base`
` def filename`
`"#{model.attachmentable.name}-REV##{model.attachmentable.ver}-SN##{model.attachmentable.doc.sn}.#{file.extension}".to_s.underscore`
`end`
`end`

But the result is that the file is saved in the old name and in the new DB name.

Start with the reported Attachment and AttachmentUploader examples, especially duplicate_file and the uploader filename method. Reproduce the copy with CarrierWave and compare the stored file name with the database value; done means the copied file is stored under the new name without leaving the old-named copy.

Written by the indexing model from the issue text.