code: def guess_url_vcs(url):
      
      parsed = urllib.parse.urlsplit(url)
  
      if parsed.scheme in ('git', 'svn'):
          return parsed.scheme
      elif parsed.path.endswith('.git'):
          return 'git'
      elif parsed.hostname == 'github.com':
          return 'git'
  
      # If it's an http url, we can try requesting it and guessing from the
      # contents.
      if parsed.scheme in ('http', 'https'):
          resp = requests.get(url)
          if re.match('basehttp.*python.*', resp.headers.get('server').lower()):
              # It's the mercurial http server
              return 'hg'
      return None
docs: Given a url, try to guess what kind of VCS it's for.  Return None if we
      can't make a good guess.