Python script to rename alembic migration files after `file_template` configuration option is changed from default one

rename_alembic_migrations.py

"""
Copyright (c) 2024 Vitaly Samigullin

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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### Rename alembic migration files ###

This Python script renames Alembic migration files that followed 
the default naming convention from the `alembic.ini`:

```
[alembic]
script_location = migrations
# 415d16af53f6_test_migrations.py
file_template = %%(rev)s_%%(slug)s
```

to the new file name format:

```
[alembic]
script_location = migrations
# 2024_05_02_1011-415d16af53f6_test_migrations.py
file_template = %%(year)d_%%(month).2d_%%(day).2d_%%(hour).2d%%(minute).2d-%%(rev)s_%%(slug)s
```

Renaming migration files doesn't affect the migration themselves:
https://stackoverflow.com/questions/35672933/does-alembic-care-what-its-migration-files-are-called

So, it's nice to keep things tidy!
"""

import ast
import datetime
import re
import os
import unicodedata


migrations = os.path.dirname("./migrations/versions/")

def slugify(value, length=40):
    value = unicodedata.normalize('NFKD', value).encode('ascii', 'ignore').decode('ascii')
    value = re.sub('[^\w\s-]', '', value).strip().lower()
    result = re.sub('[-\s]+', '_', value)

    if length is not None:
        return result[:length]
    return result


for migration in os.listdir(migrations):
    old_file_path = os.path.join(migrations, migration)
    if os.path.isdir(old_file_path):
        continue

    old_file_name_no_ext = migration.rstrip(".py")

    with open(old_file_path) as f:
        content = f.read()
        parsed = ast.parse(content)
        docstring = ast.get_docstring(parsed)

        message, _, revision, revises, ts = docstring.split("\n")
        message_trunc = slugify(value=message, length=40)

        revision_id = re.sub('Revision ID: ', '', revision)

        if migration == "{}_.py".format(revision_id):
            slug = message_trunc
        else:
            slug = ""

        dt_str = re.sub('Create Date: ', '', ts)
        dt = datetime.datetime.strptime(dt_str, '%Y-%m-%d %H:%M:%S.%f')
        new_dt_str = dt.strftime("%Y_%m_%d_%H%M")
        
    new_file_name = "{dt}-{old}{slug}.py".format(dt=new_dt_str, old=old_file_name_no_ext, slug=slug)
    new_file_path = os.path.join(migrations, new_file_name)
    os.rename(old_file_path, new_file_path)