Use MigrationLoader to order migrations

[q0w]

Fix #161

What do you think @adamchainz? It also seems using MigrationLoader needs proper fake migrations (with Migration class, not just empty files)

[q0w]

its just a copy of https://github.com/django/django/blob/main/django/db/migrations/graph.py#L306 (with passing at_end=True)

[adamchainz]

I'd feel more comfortable calling the method in Django, even if it is private.

[q0w]

ok, i will use typing.cast to avoid Any

[adamchainz]

Looks like a good start. (Please don't create draft PR's if you want them looked at, "draft" normally means "don't look at this".)

In the issue I noted we'd need to call detect_conflicts().

The test run failures are due to lack of Migration which you said.

Will you keep working on this?

[q0w]

Yea, i am going to rewrite tests.
Where should it call detect_conflicts and how it should be handled?

[q0w]

I've added dlm.E000 as Error for conflicts in the migration graph.

[adamchainz]

Just getting round to this now after a busy end of 2022...

Please, whenever you open an open source PR, update the documentation and add a changelog note.

[q0w]

What do you think about adding a new flag to provide the db name instead of using always DB_DEFAULT_ALIAS in MigrationLoader?

[adamchainz]

It seems we can use None for connection and skip loading migration state from the database entirely: https://github.com/django/django/blob/898f0aa44fe63c20d7f4125672b8eb800a578ce5/django/db/migrations/loader.py#L230-L235

[adamchainz]

Released in 2.6.0, thanks!