rn.py

import re
import sys
import os

for path in sys.argv[1:]:
    with open(path) as f:
        contents = f.read()
    m = re.search(r'created_at: (.*)', contents)
    d, m, y = map(int, m.group(1).split('/'))

    fn = os.path.basename(path)
    base, _ = fn.split('.')
    newfn = '{:04d}-{:02d}-{:02d}-{}.md'.format(y, m, d, base)

    print('{} -> {}'.format(fn, newfn))

    new_contents = re.sub(r'created_at: .*', 'layout: post', contents)
    with open(newfn, 'w') as f:
        f.write(new_contents)