Fixed #26429 -- Added a timestamp to merge migration names.

This reduces the possibility of a naming conflict, especially after
squashing migrations.

django/core/management/__init__.py

@@ -76,7 +76,7 @@ def get_commands():
     return commands
 
 
-def call_command(name, *args, **options):
+def call_command(command_name, *args, **options):
     """
     Calls the given command, with the given options and args/kwargs.
 
@@ -95,25 +95,25 @@ def call_command(name, *args, **options):
         call_command(cmd, verbosity=0, interactive=False)
         # Do something with cmd ...
     """
-    if isinstance(name, BaseCommand):
+    if isinstance(command_name, BaseCommand):
         # Command object passed in.
-        command = name
-        name = command.__class__.__module__.split('.')[-1]
+        command = command_name
+        command_name = command.__class__.__module__.split('.')[-1]
     else:
         # Load the command object by name.
         try:
-            app_name = get_commands()[name]
+            app_name = get_commands()[command_name]
         except KeyError:
-            raise CommandError("Unknown command: %r" % name)
+            raise CommandError("Unknown command: %r" % command_name)
 
         if isinstance(app_name, BaseCommand):
             # If the command is already loaded, use it directly.
             command = app_name
         else:
-            command = load_command_class(app_name, name)
+            command = load_command_class(app_name, command_name)
 
     # Simulate argument parsing to get the option defaults (see #10080 for details).
-    parser = command.create_parser('', name)
+    parser = command.create_parser('', command_name)
     # Use the `dest` option name from the parser option
     opt_mapping = {
         sorted(s_opt.option_strings)[0].lstrip('-').replace('-', '_'): s_opt.dest

django/core/management/commands/makemigrations.py

@@ -14,6 +14,7 @@ from django.db.migrations.questioner import (
     NonInteractiveMigrationQuestioner,
 )
 from django.db.migrations.state import ProjectState
+from django.db.migrations.utils import get_migration_name_timestamp
 from django.db.migrations.writer import MigrationWriter
 from django.utils.deprecation import RemovedInDjango20Warning
 from django.utils.six import iteritems
@@ -283,7 +284,11 @@ class Command(BaseCommand):
                 subclass = type("Migration", (Migration, ), {
                     "dependencies": [(app_label, migration.name) for migration in merge_migrations],
                 })
-                new_migration = subclass("%04i_merge" % (biggest_number + 1), app_label)
+                migration_name = "%04i_%s" % (
+                    biggest_number + 1,
+                    self.migration_name or ("merge_%s" % get_migration_name_timestamp())
+                )
+                new_migration = subclass(migration_name, app_label)
                 writer = MigrationWriter(new_migration)
 
                 if not self.dry_run:

django/db/migrations/autodetector.py

@@ -1,6 +1,5 @@
 from __future__ import unicode_literals
 
-import datetime
 import functools
 import re
 from itertools import chain
@@ -12,7 +11,9 @@ from django.db.migrations.migration import Migration
 from django.db.migrations.operations.models import AlterModelOptions
 from django.db.migrations.optimizer import MigrationOptimizer
 from django.db.migrations.questioner import MigrationQuestioner
-from django.db.migrations.utils import COMPILED_REGEX_TYPE, RegexObject
+from django.db.migrations.utils import (
+    COMPILED_REGEX_TYPE, RegexObject, get_migration_name_timestamp,
+)
 from django.utils import six
 
 from .topological_sort import stable_topological_sort
@@ -1154,7 +1155,7 @@ class MigrationAutodetector(object):
         elif len(ops) > 1:
             if all(isinstance(o, operations.CreateModel) for o in ops):
                 return "_".join(sorted(o.name_lower for o in ops))
-        return "auto_%s" % datetime.datetime.now().strftime("%Y%m%d_%H%M")
+        return "auto_%s" % get_migration_name_timestamp()
 
     @classmethod
     def parse_number(cls, name):

django/db/migrations/utils.py

@@ -1,3 +1,4 @@
+import datetime
 import re
 
 COMPILED_REGEX_TYPE = type(re.compile(''))
@@ -10,3 +11,7 @@ class RegexObject(object):
 
     def __eq__(self, other):
         return self.pattern == other.pattern and self.flags == other.flags
+
+
+def get_migration_name_timestamp():
+    return datetime.datetime.now().strftime("%Y%m%d_%H%M")