git-send-email: use compose-encoding for Subject

The commit "git-send-email: introduce compose-encoding" introduced
the compose-encoding option to specify the introduction email encoding
(--compose option), but the email Subject encoding was still hardcoded
to UTF-8.

Signed-off-by: Krzysztof Mazur <krzysiek@podlesie.net>
Signed-off-by: Jeff King <peff@peff.net>

git-send-email.perl

@@ -636,15 +636,15 @@ sub get_patch_subject {
 	my $need_8bit_cte = file_has_nonascii($compose_filename);
 	my $in_body = 0;
 	my $summary_empty = 1;
+	if (!defined $compose_encoding) {
+		$compose_encoding = "UTF-8";
+	}
 	while(<$c>) {
 		next if m/^GIT:/;
 		if ($in_body) {
 			$summary_empty = 0 unless (/^\n$/);
 		} elsif (/^\n$/) {
 			$in_body = 1;
-			if (!defined $compose_encoding) {
-				$compose_encoding = "UTF-8";
-			}
 			if ($need_8bit_cte) {
 				print $c2 "MIME-Version: 1.0\n",
 					 "Content-Type: text/plain; ",
@@ -658,7 +658,7 @@ sub get_patch_subject {
 			my $subject = $initial_subject;
 			$_ = "Subject: " .
 				($subject =~ /[^[:ascii:]]/ ?
-				 quote_rfc2047($subject) :
+				 quote_rfc2047($subject, $compose_encoding) :
 				 $subject) .
 				"\n";
 		} elsif (/^In-Reply-To:\s*(.+)\s*$/i) {

t/t9001-send-email.sh

@@ -909,6 +909,20 @@ test_expect_success $PREREQ '--compose-encoding overrides sendemail.composeencod
 	grep "^Content-Type: text/plain; charset=iso-8859-2" msgtxt1
 '
 
+test_expect_success $PREREQ '--compose-encoding adds correct MIME for subject' '
+	clean_fake_sendmail &&
+	  GIT_EDITOR="\"$(pwd)/fake-editor\"" \
+	  git send-email \
+	  --compose-encoding iso-8859-2 \
+	  --compose --subject utf8-sübjëct \
+	  --from="Example <nobody@example.com>" \
+	  --to=nobody@example.com \
+	  --smtp-server="$(pwd)/fake.sendmail" \
+	  $patches &&
+	grep "^fake edit" msgtxt1 &&
+	grep "^Subject: =?iso-8859-2?q?utf8-s=C3=BCbj=C3=ABct?=" msgtxt1
+'
+
 test_expect_success $PREREQ 'detects ambiguous reference/file conflict' '
 	echo master > master &&
 	git add master &&