trailer: retitle a test and correct an in-comment message

Signed-off-by: Christian Couder <christian.couder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t7513-interpret-trailers.sh

diff --git a/t/t7513-interpret-trailers.sh b/t/t7513-interpret-trailers.sh
index 33cf4d1..8f1f55b 100755
--- a/t/t7513-interpret-trailers.sh
+++ b/t/t7513-interpret-trailers.sh
@@ -99,7 +99,7 @@
 	test_cmp expected actual
 '
 
-test_expect_success 'with message that contains only a title' '
+test_expect_success 'with only a title in the message' '
 	cat >expected <<-\EOF &&
 		area: change
 

trailer.c

diff --git a/trailer.c b/trailer.c
index f7d2713..a92ba53 100644
--- a/trailer.c
+++ b/trailer.c
@@ -748,7 +748,8 @@
 	/*
 	 * Get the start of the trailers by looking starting from the end
 	 * for a line with only spaces before lines with one separator.
-	 * The start cannot be the first line.
+	 * The first line must not be analyzed as the others as it
+	 * should be either the message title or a blank line.
 	 */
 	for (start = count - 1; start >= 1; start--) {
 		if (lines[start]->buf[0] == comment_line_char)