docs: def github_signature(string, shared_secret, challenge_hmac):
      '''
      Verify a challenging hmac signature against a string / shared-secret for
      github webhooks.
  
      .. versionadded:: 2017.7.0
  
      Returns a boolean if the verification succeeded or failed.
  
      CLI Example:
  
      .. code-block:: bash
  
          salt '*' hashutil.github_signature '{"ref":....} ' 'shared secret' 'sha1=bc6550fc290acf5b42283fa8deaf55cea0f8c206'
      '''
      msg = string
      key = shared_secret
      hashtype, challenge = challenge_hmac.split('=')
      if six.text_type:
          msg = salt.utils.stringutils.to_bytes(msg)
          key = salt.utils.stringutils.to_bytes(key)
      hmac_hash = hmac.new(key, msg, getattr(hashlib, hashtype))
      return hmac_hash.hexdigest() == challenge