Django Auto Rebase

What is this?

This is a command-line tool that allows you to rebase a conflicting Django migration on top of the other Django migration renaming (and renumbering) the migration filename and also editing the dependencies attribute on the Migration class within the file.

Installation

$ pip install django-auto-rebase

Usage

$ dar [app-name] [migration-file-to-be-rebased]

Requirements

• Python 3.7 (for now. file an issue if you need an earlier version supported)
• Django 2.2 (earlier versions will likely work, but it's untested for now.

Limitations

• Only works on leaf nodes that have migration conflicts.
• Only works on leaf nodes within the same app.

FAQ

Is this a Django Command?

No, although this package is tightly coupled to Django, it is NOT a Django app that you need to add to your INSTALLED_APPS or call through a manage.py.

How does it find the root Django path?

The first thing the script does after parsing your arguments is it walks up the current working directory until it finds the manage.py file that all if not most Django applications have. The folder that holds the first manage.py directory is appended to sys.path.

Why do you even need this?

Well, you don't really need it, but I find it helpful.

Suppose the migration tree looks like this:

0001_xxx <-- 0002_xxx <-- 0003_xxx

Then two developers, working in separate branches, generate their own 0004_xxx migration. Once the first developer gets their code merged to master, the second developer's migration tree is immediately stale/in conflict because its 0004_xxx will still be pointing at 0003_xxx as a dependency. You may find yourself getting this error message:

Conflicting migrations detected; multiple leaf nodes in the migration graph:
(0004_xxx, 0004_yyy in my_app_name).
To fix them run 'python manage.py makemigrations --merge'

As the message suggests, you could run makemigrations --merge, which generates a new leaf node 0005_xxx and specifies the two 0004_xxx migrations as a dependencies. This works in small doses, but I'm not a huge fan. (see below)

What's wrong with makemigrations --merge?

The magic numbers of each migration starts meaning less and less.

Strictly speaking, they really do mean nothing - Django doesn't care at all about the number: A 0004_xxx migration could depend on a migration named 9999_xxx, which depends on 1234_xxx.

Practically speaking, I do find value in seeing the dependency order of the migration tree follow their actual numbers. This tool helps rebase two conflicting migrations with ease.

Author

Christopher Sabater Cordero