makemigrations --update changes the name of custom migration name

[David Sanders]

This may be intentional behaviour but the docs don't mention this so creating a ticket to update docs or correct behaviour:

If you create a migration with a custom name:

$ ./manage.py makemigrations --name foo
Migrations for 'update_rename':
  update_rename/migrations/0001_foo.py
    - Create model Foo

then running --update will change the name "foo" to the autogenerated one based on the operations:

$ ./manage.py makemigrations --update
Migrations for 'update_rename':
  update_rename/migrations/0001_initial.py
    - Create model Foo
Deleted update_rename/migrations/0001_foo.py

My opinion is that it shouldn't as it violates the principle of least astonishment even though the --name argument wasn't supplied.

EDIT:
This is my first time using --update and here are a few other observations which could indicate that it requires broader discussion:

• It doesn't utilise the --name argument so it's impossible to customise the name during --update
• It'd be nice to provide --no-optimize option to --update, here's my use-case: 3-step non-null field addition. After doing nullable step 1, elidable data migration step 2, I want to merge the step 3 non-null update into the migration but --update optimizes this into a single step.

Perhaps --update requires a rethink?

[David Sanders]

<moved to description>