Django - Avoid duplicate in migration names before committing changes in Git

git-pre-commit-hook-django-migrations

#!/usr/bin/python
"""
    Pre-commit hook for git written in Python.
    Check if there is any migration number used more than one in each
    migrations folder of South or Django >= 1.7.
    You can install this pre-hook by executing the command:
        ln -s ./git-pre-commit-hook .git/hooks/pre-commit
        chmod +x .git/hooks/pre-commit
    Or by calling the current script or check_migrations_files() in your
    own file.
    By Maxime Lorant <[email protected]> Free for any use (BSD)
"""
import subprocess
import sys
from collections import Counter, defaultdict


def check_migrations_files():
    """ Check if migrations names does not clash (e.g. two with the same number) """

    # Get migrations files in a list
    migrations = subprocess.check_output("git ls-files -- $(find . -type d -iname migrations)", shell=True)
    migrations = migrations.decode().split('\n')

    by_folders = defaultdict(list)
    for migration in migrations:
        # Skip empty lines and __init__ file
        if '/' in migration:
            path, filename = migration.rsplit('/', 1)
            if filename != '__init__.py':
                # Filename format: xxxx_name_of_the_migration. We keep only `xxxx`
                number, _ = filename.split('_', 1)
                by_folders[path].append(number)

    # For each folder we get the list of items
    for key, lst in by_folders.items():
        duplicated = [x for x, y in Counter(lst).items() if y > 1]

        # Check if there is any duplicate
        if duplicated:
            duplicated_string = ','.join(duplicated)
            print("At least two migrations has the same number ({}) in \033[1m{}\033[0m."
                  "\nPlease fix this before committing your changes.".format(duplicated_string, key))

            sys.exit(-1)


if __name__ == "__main__":
    check_migrations_files()