Some MTAs reject Cc: lines longer than 78 chars.
Avoid this by using the same join as "To:" ",\n\t"
so each subsequent Cc entry is on a new line.

RCPT TO: should have a single entry per line.
see: http://www.ietf.org/rfc/rfc2821.txtSigned-off-by: NJoe Perches <joe@perches.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>