send-email: restore --in-reply-to superseding behavior

git send-email --in-reply-to= fails to override In-Reply-To email headers,
if they're present in the output of format-patch, even when explicitly
told to do so by the option --no-thread, which breaks the contract of the
command line switch option, per its man page.

"
   --in-reply-to=<identifier>
       Make the first mail (or all the mails with --no-thread) appear as
       a reply to the given Message-Id, which avoids breaking threads to
       provide a new patch series.
"

This patch fixes the aformentioned issue, by bringing --in-reply-to's old
overriding behavior back.

The test was donated by Carlo Marcelo Arenas Belón.

Signed-off-by: Rafael Aquini <aquini@redhat.com>
Helped-by: Carlo Marcelo Arenas Belón <carenas@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 6 insertions, 2 deletions

diff --git a/git-send-email.perl b/git-send-email.perl
index dc95656..36c47ba 100755
--- a/git-send-email.perl
+++ b/git-send-email.perl
@@ -1699,10 +1699,14 @@ sub process_file {
 				$xfer_encoding = $1 if not defined $xfer_encoding;
 			}
 			elsif (/^In-Reply-To: (.*)/i) {
-				$in_reply_to = $1;
+				if (!$initial_in_reply_to || $thread) {
+					$in_reply_to = $1;
+				}
 			}
 			elsif (/^References: (.*)/i) {
-				$references = $1;
+				if (!$initial_in_reply_to || $thread) {
+					$references = $1;
+				}
 			}
 			elsif (!/^Date:\s/i && /^[-A-Za-z]+:\s+\S/) {
 				push @xh, $_;