put sample code in empty migrations

[Chris Curvey]

SHORT VERSION: put sample code into the generated file when creating an "empty" migration, like this:

#def combine_names(apps, schema_editor):
# # We can't import the Person model directly as it may be a newer
# # version than this migration expects. We use the historical version.
# Person = apps.get_model('yourappname', 'Person')
# for person in Person.objects.all():
# person.name = '%s %s' % (person.first_name, person.last_name)
# person.save()

and then

operations = [

#migrations.RunPython(combine_names),

]

LONG VERSION/JUSTIFICATION:

Every time I create a data migration (python manage.py makemigrations foo --empty), I have to do a web search to remember what the parameters are to the function I want to call (apps, schema_editor), and how to use those parameters, and how to get the code to actually run (migrations.RunPython).

It would be really nice to have that sample code just put into the empty migration so that it is there as an example.