[1.8.x] Fixed #24184 -- Prevented automatic soft-apply of migrations

Previously Django only checked for the table name in CreateModel
operations in initial migrations and faked the migration automatically.
This led to various errors and unexpected behavior. The newly introduced
--fake-initial flag to the migrate command must be passed to get the
same behavior again. With this change Django will bail out in with a
"duplicate relation / table" error instead.

Thanks Carl Meyer and Tim Graham for the documentation update, report
and review.

Backport of f287bec583 from master

django/db/migrations/executor.py

@@ -62,7 +62,7 @@ class MigrationExecutor(object):
                         applied.add(migration)
         return plan
 
-    def migrate(self, targets, plan=None, fake=False):
+    def migrate(self, targets, plan=None, fake=False, fake_initial=False):
         """
         Migrates the database up to the given targets.
 
@@ -91,7 +91,7 @@ class MigrationExecutor(object):
         # Phase 2 -- Run the migrations
         for migration, backwards in plan:
             if not backwards:
-                self.apply_migration(states[migration], migration, fake=fake)
+                self.apply_migration(states[migration], migration, fake=fake, fake_initial=fake_initial)
             else:
                 self.unapply_migration(states[migration], migration, fake=fake)
 
@@ -113,18 +113,19 @@ class MigrationExecutor(object):
             statements.extend(schema_editor.collected_sql)
         return statements
 
-    def apply_migration(self, state, migration, fake=False):
+    def apply_migration(self, state, migration, fake=False, fake_initial=False):
         """
         Runs a migration forwards.
         """
         if self.progress_callback:
             self.progress_callback("apply_start", migration, fake)
         if not fake:
-            # Test to see if this is an already-applied initial migration
-            applied, state = self.detect_soft_applied(state, migration)
-            if applied:
-                fake = True
-            else:
+            if fake_initial:
+                # Test to see if this is an already-applied initial migration
+                applied, state = self.detect_soft_applied(state, migration)
+                if applied:
+                    fake = True
+            if not fake:
                 # Alright, do it normally
                 with self.connection.schema_editor() as schema_editor:
                     state = migration.apply(state, schema_editor)