Merge branch 'cl/send-email-reply-to'

"git send-email" learned "--reply-to=<address>" option.

* cl/send-email-reply-to:
  send-email: support separate Reply-To address
  send-email: rename variable for clarity

diff --cc contrib/completion/git-completion.bash
Simple merge

diff --cc git-send-email.perl
Simple merge

diff --cc t/t9001-send-email.sh
Simple merge