sexy_query

SELECT email
FROM (
  SELECT
    JSON_EXTRACT(payload, '$.commits'),
    REGEXP_EXTRACT(
      SPLIT(
        JSON_EXTRACT(payload, '$.commits'),
        '},{'
      ),
      r'email":([^,]+),'
    )
  AS email
  FROM [githubarchive:month.201501]
  WHERE type = 'PushEvent'
)
GROUP BY
  email
LIMIT 1