Refs 430 on redmine, adds the ability to sync file deletion between recurring events.

When you delete a file from an event, instead of an alert confirmation it uses a Bootstrap modal dialog so that if there is a recurring event attached, it will present the user with a list of recurring events. The user can select which of these events he or she would also like to delete the selected files from before confirming the delete action.

The only issue is that the list of recurring events to delete from is static, so if the user tries to delete an unsynced file but the event has recurring events associated, it will still present the user with the list of events. This could be changed in the future to an ajax call that dynamically chooses the content of the dialog.