add safemigrate command (#5781)

manage.py "safely" migrate a projet :
* syncdb
* for each app installed, with migrations available but never migrated:
        migrate --fake <app> 0001
* migrate

entrouvert/djommon/safemigrate/management/commands/safemigrate.py

@@ -0,0 +1,76 @@
+from django.core.management.base import NoArgsCommand
+from django.db import connections, router, models
+
+from south.models import MigrationHistory
+from south.management.commands import syncdb, migrate
+from django.core.management.commands import syncdb as django_syncdb
+
+
+class Command(NoArgsCommand):
+    option_list = django_syncdb.Command.option_list
+    help = '''syncdb + migrate, with "migrate --fake app 0001" for apps with new initial migrations'''
+
+    def handle_noargs(self, *args, **options):
+
+        # step 1 : syncdb, create all apps without migrations
+        syncdb.Command().execute(migrate_all=False, migrate=False, **options)
+
+        # step 2 : detect and "fake 0001" all installed apps that had never
+        # migrated (applications in database but not in south history)
+
+        # detect installed models
+        # (code borrowed from django syncdb command)
+        db = options.get('database')
+        connection = connections[db]
+        cursor = connection.cursor()
+        tables = connection.introspection.table_names()
+        def model_in_database(model):
+            opts = model._meta
+            converter = connection.introspection.table_name_converter
+            return (converter(opts.db_table) in tables) or \
+                (opts.auto_created and converter(opts.auto_created._meta.db_table) in tables)
+
+        # list all applications with south migration
+        # (code borrowed from south migrate command)
+        from south import migration
+        apps = list(migration.all_migrations())
+        applied_migrations = MigrationHistory.objects.filter(app_name__in=[app.app_label() for app in apps])
+        applied_migrations_lookup = dict(('%s.%s' % (mi.app_name, mi.migration), mi) for mi in applied_migrations)
+
+        print
+        print 'Status after syncdb:'
+
+        for app in apps:
+            # for each app with migrations, list already applied migrations
+            applied_migrations = []
+            for migration in app:
+                full_name = migration.app_label() + "." + migration.name()
+                if full_name in applied_migrations_lookup:
+                    applied_migration = applied_migrations_lookup[full_name]
+                    if applied_migration.applied:
+                        applied_migrations.append(migration.name())
+
+            # try all models in database, if there none, the application is new
+            # (because south syncdb does not create any tables)
+            new = True
+            for m in models.get_models(app.get_application().models):
+                if model_in_database(m):
+                    new = False
+                    break
+
+            if new:
+                status = 'application-is-new'
+            elif not applied_migrations:
+                status = 'migration-is-new'
+            else:
+                status = 'normal'
+
+            print ' - %s: %s' % (app.app_label(), status)
+
+            if status == 'migration-is-new':
+                print '   need fake migration to 0001_initial'
+                # migrate --fake gdc 0001
+                migrate.Command().execute(app=app.app_label(), target='0001', fake=True)
+
+        print
+        migrate.Command().execute(**options)