Merge branch 'km/send-email-compose-encoding'

"git send-email --compose" can let the user create a non-ascii cover letter message, but there was not a way to mark it with appropriate content type before sending it out. Further updates fix subject quoting. * km/send-email-compose-encoding: git-send-email: add rfc2047 quoting for "=?" git-send-email: introduce quote_subject() git-send-email: skip RFC2047 quoting for ASCII subjects git-send-email: use compose-encoding for Subject git-send-email: introduce compose-encoding