Show a diff between two models

Usage

luna_diff(id, reference = NULL, folder = NULL, verbose = TRUE)

id: either a single id or a vector of exactly two model ids. If specified as a single value, the id needs to have a reference model specified to which it can be compared. If id is of length 2, then it will just diff the models for the two ids.
reference: id for reference model to compare to (optional)
folder: path to folder containing the model file. Default is current directory.