* mh/fix-send-email-threaded:
send-email: fix a typo in a comment
send-email: fix threaded mails without chain-reply-to
add a test for git-send-email for threaded mails without chain-reply-to
doc/send-email: clarify the behavior of --in-reply-to with --no-thread
send-email: fix non-threaded mails
add a test for git-send-email for non-threaded mails