pretty, ref-filter: format %(trailers) with no_divider option

In both of these cases we know that we are feeding the
trailer-parsing code a pure commit message. We should tell
it so, which avoids false positives for a commit message
that contains a "---" line.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

pretty.c

@@ -1304,6 +1304,9 @@ static size_t format_commit_one(struct strbuf *sb, /* in UTF-8 */
 
 	if (skip_prefix(placeholder, "(trailers", &arg)) {
 		struct process_trailer_options opts = PROCESS_TRAILER_OPTIONS_INIT;
+
+		opts.no_divider = 1;
+
 		if (*arg == ':') {
 			arg++;
 			for (;;) {

ref-filter.c

@@ -223,6 +223,8 @@ static int trailers_atom_parser(const struct ref_format *format, struct used_ato
 	struct string_list params = STRING_LIST_INIT_DUP;
 	int i;
 
+	atom->u.contents.trailer_opts.no_divider = 1;
+
 	if (arg) {
 		string_list_split(&params, arg, ',', -1);
 		for (i = 0; i < params.nr; i++) {

t/t4205-log-pretty-formats.sh

@@ -598,4 +598,27 @@ test_expect_success ':only and :unfold work together' '
 	test_cmp expect actual
 '
 
+test_expect_success 'trailer parsing not fooled by --- line' '
+	git commit --allow-empty -F - <<-\EOF &&
+	this is the subject
+
+	This is the body. The message has a "---" line which would confuse a
+	message+patch parser. But here we know we have only a commit message,
+	so we get it right.
+
+	trailer: wrong
+	---
+	This is more body.
+
+	trailer: right
+	EOF
+
+	{
+		echo "trailer: right" &&
+		echo
+	} >expect &&
+	git log --no-walk --format="%(trailers)" >actual &&
+	test_cmp expect actual
+'
+
 test_done

t/t6300-for-each-ref.sh

@@ -715,6 +715,29 @@ test_expect_success 'basic atom: head contents:trailers' '
 	test_cmp expect actual.clean
 '
 
+test_expect_success 'trailer parsing not fooled by --- line' '
+	git commit --allow-empty -F - <<-\EOF &&
+	this is the subject
+
+	This is the body. The message has a "---" line which would confuse a
+	message+patch parser. But here we know we have only a commit message,
+	so we get it right.
+
+	trailer: wrong
+	---
+	This is more body.
+
+	trailer: right
+	EOF
+
+	{
+		echo "trailer: right" &&
+		echo
+	} >expect &&
+	git for-each-ref --format="%(trailers)" refs/heads/master >actual &&
+	test_cmp expect actual
+'
+
 test_expect_success 'Add symbolic ref for the following tests' '
 	git symbolic-ref refs/heads/sym refs/heads/master
 '