Merge branch 'ra/send-email-in-reply-to-from-command-line-wins' into master

"git send-email --in-reply-to=<msg>" did not use the In-Reply-To: header with the value given from the command line, and let it be overridden by the value on In-Reply-To: header in the messages being sent out (if exists). * ra/send-email-in-reply-to-from-command-line-wins: send-email: restore --in-reply-to superseding behavior