Fixed #24529 -- Allowed double squashing of migrations.

Co-authored-by: Raphael Gaschignard <raphael@rtpg.co>

tests/migrations/test_migrations_squashed_partially_applied/0001_initial.py

@@ -0,0 +1,35 @@
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+    operations = [
+        migrations.CreateModel(
+            name="MyModel1",
+            fields=[
+                (
+                    "id",
+                    models.BigAutoField(
+                        auto_created=True,
+                        primary_key=True,
+                        serialize=False,
+                        verbose_name="ID",
+                    ),
+                ),
+            ],
+        ),
+        migrations.CreateModel(
+            name="MyModel2",
+            fields=[
+                (
+                    "id",
+                    models.BigAutoField(
+                        auto_created=True,
+                        primary_key=True,
+                        serialize=False,
+                        verbose_name="ID",
+                    ),
+                ),
+                ("field_1", models.IntegerField()),
+            ],
+        ),
+    ]

tests/migrations/test_migrations_squashed_partially_applied/0002_mymodel1_field_1_mymodel2_field_2_and_more.py

@@ -0,0 +1,23 @@
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+    dependencies = [("migrations", "0001_initial")]
+
+    operations = [
+        migrations.AddField(
+            model_name="mymodel1",
+            name="field_1",
+            field=models.IntegerField(null=True),
+        ),
+        migrations.AddField(
+            model_name="mymodel2",
+            name="field_2",
+            field=models.IntegerField(null=True),
+        ),
+        migrations.AlterField(
+            model_name="mymodel2",
+            name="field_1",
+            field=models.IntegerField(null=True),
+        ),
+    ]

tests/migrations/test_migrations_squashed_partially_applied/0003_alter_mymodel2_unique_together.py

@@ -0,0 +1,12 @@
+from django.db import migrations
+
+
+class Migration(migrations.Migration):
+    dependencies = [("migrations", "0002_mymodel1_field_1_mymodel2_field_2_and_more")]
+
+    operations = [
+        migrations.AlterUniqueTogether(
+            name="mymodel2",
+            unique_together={("field_1", "field_2")},
+        ),
+    ]

tests/migrations/test_migrations_squashed_partially_applied/0004_remove_mymodel1_field_1_mymodel1_field_3_and_more.py

@@ -0,0 +1,22 @@
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+    dependencies = [("migrations", "0003_alter_mymodel2_unique_together")]
+
+    operations = [
+        migrations.RemoveField(
+            model_name="mymodel1",
+            name="field_1",
+        ),
+        migrations.AddField(
+            model_name="mymodel1",
+            name="field_3",
+            field=models.IntegerField(null=True),
+        ),
+        migrations.AddField(
+            model_name="mymodel1",
+            name="field_4",
+            field=models.IntegerField(null=True),
+        ),
+    ]