Prepare for syntax change in urls.md

[StoneyJackson]

We are planning to change the format of urls.md. It will contain more data than just URLs. Something like this would probably do for now

import re
def parse_urls_md(lines):
  url_pattern = re.compile(r'- +(http.*\.git)')
  urls = []
  for line in lines:
    line = line.strip()
    match = url_pattern.search(line)
    if match is not None:
      urls.append(match.group(1))
  return urls

The regex can be tuned later if it turns out to be insufficient.