Minor Description
The Tika MIME detector recognizes a robots.txt file as "message/rfc822" if the file starts with a "User-Agent" rule and contains also a second rule not too far away from the beginning, e.g.:
User-Agent: goodbot Disallow: User-Agent: badbot Disallow: /
The change 7769a2b requires that two different clauses are matched. However, the two occurrences of "User-Agent:" (initial and after a new line) are treated as different instead of equivalent matches.