Takes the full name of a python module as argument. It then imports this module and expects it to define a function objects in its global namespace. It calls this function and expects it to yield a series of Django instance objects which have not yet been saved. It then compares these objects with the "corresponding data" in the database and prints a summary to stdout. It then suggests to merge the new data into the database.
It never deletes any stored records.
All incoming objects either replace an existing (stored) object, or will be added to the database.
If an incoming object has a non-empty primary key, then it replaces the corresponding stored object. Otherwise, if the model has unique fields, then these cause potential replacement.
Currently the command is only partly implemented, it doesn't yet update existing records. But it detects whether records are new, and adds only those.
(This module's source code is available here.)