post-checkout

#!/usr/bin/env python
import re
import sys
import subprocess
from collections import defaultdict

MIGRATION_REGEX = r'.+\/(?P<app>.+)\/migrations\/(?P<num>\d{4})_.+.py'

fn, previous_head, current_head, is_branch = sys.argv
if not is_branch == '1' or previous_head == current_head:
    sys.exit(0)

revert_map, run_map = {}, {}
diff = defaultdict(list)
output = subprocess.check_output(
    'git --no-pager diff --name-status %s %s ' % (
        previous_head, current_head), shell=True)


for i in output.decode().split('\n'):
    if not i:
        continue
    op, fname = i.split('\t')
    diff[op].append(fname)


for path in diff.get('D', []):
    match = re.match(MIGRATION_REGEX, path)
    if match:
        data = match.groupdict()
        if data['app'] not in revert_map or int(data['num']) < int(revert_map[data['app']]):
            revert_map[data['app']] = data['num']


for path in diff.get('A', []):
    match = re.match(MIGRATION_REGEX, path)
    if match:
        data = match.groupdict()
        if data['app'] not in run_map or int(data['num']) > int(run_map[data['app']]):
            run_map[data['app']] = data['num']


if revert_map:
    print('\nATTENTION!!!\n'
          'You have deleted migrations in this branch.\n'
          'You may need to return to the previous one and revert those:')
    for key, value in revert_map.items():
        value = int(value) - 1
        if value == 0:
            value = 'zero'
        print('./manage.py migrate {} {:0>4}'.format(key, value))


if run_map:
    print('You have new migrations in this branch:')
    for key, value in run_map.items():
        print('./manage.py migrate {} {}'.format(key, value))