sequencer: reencode squashing commit's message

On fixup/squash-ing rebase, git will create new commit in
i18n.commitencoding, reencode the commit message to that said encode.

Signed-off-by: Doan Tran Cong Danh <congdanhqx@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

sequencer.c

@@ -1576,6 +1576,7 @@ static int update_squash_messages(struct repository *r,
 	struct strbuf buf = STRBUF_INIT;
 	int res;
 	const char *message, *body;
+	const char *encoding = get_commit_output_encoding();
 
 	if (opts->current_fixup_count > 0) {
 		struct strbuf header = STRBUF_INIT;
@@ -1602,7 +1603,7 @@ static int update_squash_messages(struct repository *r,
 			return error(_("need a HEAD to fixup"));
 		if (!(head_commit = lookup_commit_reference(r, &head)))
 			return error(_("could not read HEAD"));
-		if (!(head_message = get_commit_buffer(head_commit, NULL)))
+		if (!(head_message = logmsg_reencode(head_commit, NULL, encoding)))
 			return error(_("could not read HEAD's commit message"));
 
 		find_commit_subject(head_message, &body);
@@ -1623,7 +1624,7 @@ static int update_squash_messages(struct repository *r,
 		unuse_commit_buffer(head_commit, head_message);
 	}
 
-	if (!(message = get_commit_buffer(commit, NULL)))
+	if (!(message = logmsg_reencode(commit, NULL, encoding)))
 		return error(_("could not read commit message of %s"),
 			     oid_to_hex(&commit->object.oid));
 	find_commit_subject(message, &body);
@@ -4154,9 +4155,10 @@ static int commit_staged_changes(struct repository *r,
 				 */
 				struct commit *commit;
 				const char *path = rebase_path_squash_msg();
+				const char *encoding = get_commit_output_encoding();
 
 				if (parse_head(r, &commit) ||
-				    !(p = get_commit_buffer(commit, NULL)) ||
+				    !(p = logmsg_reencode(commit, NULL, encoding)) ||
 				    write_message(p, strlen(p), path, 0)) {
 					unuse_commit_buffer(commit, p);
 					return error(_("could not write file: "

t/t3900-i18n-commit.sh

@@ -224,7 +224,15 @@ test_commit_autosquash_multi_encoding () {
 		git commit -a --$flag HEAD^ &&
 		git rebase --autosquash -i HEAD^^^ &&
 		git rev-list HEAD >actual &&
-		test_line_count = 3 actual
+		test_line_count = 3 actual &&
+		iconv -f $old -t UTF-8 "$TEST_DIRECTORY"/t3900/$msg >expect &&
+		if test $flag = squash; then
+			subject="$(head -1 expect)" &&
+			printf "\nsquash! %s\n" "$subject" >>expect
+		fi &&
+		git cat-file commit HEAD^ >raw &&
+		(sed "1,/^$/d" raw | iconv -f $new -t utf-8) >actual &&
+		test_cmp expect actual
 	'
 }