Update migration utils for improved filtering and recording.
Review Request #10578 — Created June 4, 2019 and submitted
filter_migration_targetsis now able to exclude specific targets from
the list, which is useful for filtering out already-applied migrations.
record_applied_migrationscan now record migrations for multiple apps
at a time. Previously, it took a specific app label and list of
migratino names, but now it takes a list of targets instead, making it
far more useful.
Unit tests pass on all supported versions of Django.