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Branch: main

├── app
│   ├── migrations
│   ├── 0001_initial.py
│   ├── 0002_auto_20210521_2328.py

Branch: feature/test-a

├── app
│   ├── migrations
│   ├── 0001_initial.py
│   ├── 0002_auto_20210521_2328.py
│   ├── 0003_auto_20210522_1128.py

Branch:feature/test-b

├── app
│   ├── migrations
│   ├── 0001_initial.py
│   ├── 0002_auto_20210521_2328.py
│   ├── 0003_auto_20210522_1228.py

Both feature/test-a and feature/test-b share the last migration on main (0002_auto_20210521_2328.py)

Once feature/test-a is merged into main you run into the problem of resolving migrations on feature/test-b which was dependent on 0002_auto_20210521_2328.py

Branch: main

├── app
│   ├── migrations
│   ├── 0001_initial.py
│   ├── 0002_auto_20210521_2328.py
│   ├── 0003_auto_20210522_1128.py

Branch: feature/test-b

├── app
│   ├── migrations
│   ├── 0001_initial.py
│   ├── 0002_auto_20210521_2328.py
│   ├── 0003_auto_20210522_1128.py \___________________ Both dependent on 0002_auto_20210521_2328.py
│   ├── 0003_auto_20210522_1228.py /

Running makemigrations fails with the following error:

CommandError: Conflicting migrations detected; multiple leaf nodes in the migration graph: (0003_auto_20210522_1128, 0003_auto_20210522_1228 in app).
To fix them run 'python manage.py makemigrations --merge'

Using the --merge option creates a new migration file which might not be desired.

Solution

django-migration-fixer identifies changes between the default branch main, and the feature branch feature/test-b and maintains a consistent dependency history as shown below:

Branch: feature/test-b

├── app
│   ├── migrations
│   ├── 0001_initial.py
│   ├── 0002_auto_20210521_2328.py
│   ├── 0003_auto_20210522_1128.py
│   ├── 0004_auto_20210522_1228.py  # Renames: '0003_auto_20210522_1228.py' → '0004_auto_20210522_1228.py'

0004_auto_20210522_1228.py

...
from django.db import migrations, models


class Migration(migrations.Migration):

    dependencies = [
        ('app', '0003_auto_20210522_1128'),  # Replaced '0002_auto_20210521_2328' → '0003_auto_20210522_1128'
    ]

    operations = [
        ...
    ]

NOTE: :warning:

This also works when there are conflicts detected on the default branch.

i.e You can run python manage.py makemigrations --fix on the main branch which relies on primitively picking the first migration file.

e.g (0003_auto_20210522_1128, 0003_auto_20210522_1228 in app) would result in 0003_auto_20210522_1128.py being picked as the base migration which might not be accurate in every case and is not recommended.