We add the content-type header only when we have non-7bit
characters from the 'From' header, so we really need to
specify the encoding (in other cases, where the commit text
needed a content-type, git-format-patch will already have
added the encoding header).
Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>