Returns only the sparse overrides that are actually persisted in the options file -- i.e., only non-default field values.
config.overrides(options_file_name = NULL, options_dir = NULL)[list] The sparse overrides (only non-default values).
[character, optional] The name of the options
file. If NULL (default), the user will be prompted interactively.
[character, optional] The directory containing options
files. If NULL (default), the default directory is used.