Implements the command line interface `butler make-discrete-skymap` subcommand,
should only be called by command line tools and unit test code that tests
this function.
Constructs a skymap from calibrated exposure in the butler repository
Parameters
----------
repo : `str`
URI to the location to read the repo.
config_file : `str` or `None`
URI to a config file that contains overrides to the skymap config.
collections : `list` [`str`]
An expression specifying the collections to be searched (in order) when
reading datasets, and optionally dataset type restrictions on them.
At least one collection must be specified. This is the collection
with the calibrated exposures.
instrument : `str`
The name or fully-qualified class name of an instrument.
skymap_id : `str`, optional
The identifier of the skymap to save. Default is 'discrete'.
old_skymap_id : `str`, optional
The identifer of the skymap to append to. Must differ from
``skymap_id``. Ignored unless ``config.doAppend=True``.
Definition at line 29 of file makeDiscreteSkyMap.py.