Pickling a `SimpleLazyObject` wrapping a model did not work correctly; in
particular it did not add the `_django_version` attribute added in 42736ac8.
Now it will handle this and other custom `__reduce__` methods correctly.
This commits lifts the restriction that the outermost atomic block must
be declared with savepoint=False. This restriction was overly cautious.
The logic that makes it safe not to create savepoints for inner blocks
also applies to the outermost block when autocommit is disabled and a
transaction is already active.
This makes it possible to use the ORM after set_autocommit(False).
Previously it didn't work because ORM write operations are protected
with atomic(savepoint=False).
Too much field exclusions in form's construct_instance() in _post_clean()
could lead to some unexpected missing ForeignKey values.
Fixes a regression from 45e049937. Refs #13776.
Moved data loss check when assigning to a reverse one-to-one relation on
an unsaved instance to Model.save(). This is exactly the same change as
e4b813c but for reverse relations.
With this change, it's expected to survive anything except errors
that make it impossible to import the settings. It's too complex
to fallback to a sensible behavior with a broken settings module.
Harcoding things about runserver in ManagementUtility.execute is
atrocious but it's the only way out of the chicken'n'egg problem:
the current implementation of the autoreloader primarily watches
imported Python modules -- and then a few other things that were
bolted on top of this design -- but we want it to kick in even if
the project contains import-time errors and django.setup() fails.
At some point we should throw away this code and replace it by an
off-the-shelf autoreloader that watches the working directory and
re-runs `django-admin runserver` whenever something changes.
