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

Author: gitster

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, $_;

t/t9001-send-email.sh

@@ -42,7 +42,8 @@ clean_fake_sendmail () {
 }
 
 test_expect_success $PREREQ 'Extract patches' '
-	patches=$(git format-patch -s --cc="One <[email protected]>" [email protected] -n HEAD^1)
+	patches=$(git format-patch -s --cc="One <[email protected]>" [email protected] -n HEAD^1) &&
+	threaded_patches=$(git format-patch -o threaded -s --in-reply-to="format" HEAD^1)
 '
 
 # Test no confirm early to ensure remaining tests will not hang
@@ -1219,6 +1220,17 @@ test_expect_success $PREREQ 'threading but no chain-reply-to' '
 	grep "In-Reply-To: " stdout
 '
 
+test_expect_success $PREREQ 'override in-reply-to if no threading' '
+	git send-email \
+		--dry-run \
+		--from="Example <[email protected]>" \
+		[email protected] \
+		--no-thread \
+		--in-reply-to="override" \
+		$threaded_patches >stdout &&
+	grep "In-Reply-To: <override>" stdout
+'
+
 test_expect_success $PREREQ 'sendemail.to works' '
 	git config --replace-all sendemail.to "Somebody <[email protected]>" &&
 	git send-email \