t5100: add some more mailinfo tests

Add some more simple mailinfo tests including a few that
produce:

  fatal: `pos + len' is too far after the end of the buffer

Mark those as 'test_expect_failure'.

Signed-off-by: Kyle J. McKay <mackyle@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t5100-mailinfo.sh

@@ -158,4 +158,46 @@ test_expect_success 'mailinfo handles rfc2822 comment' '
 	test_cmp "$DATA/comment.expect" comment/info
 '
 
+test_expect_success 'mailinfo no options' '
+	subj="$(echo "Subject: [PATCH] [other] [PATCH] message" |
+		git mailinfo /dev/null /dev/null)" &&
+	test z"$subj" = z"Subject: message"
+'
+
+test_expect_success 'mailinfo -k' '
+	subj="$(echo "Subject: [PATCH] [other] [PATCH] message" |
+		git mailinfo -k /dev/null /dev/null)" &&
+	test z"$subj" = z"Subject: [PATCH] [other] [PATCH] message"
+'
+
+test_expect_success 'mailinfo -b no [PATCH]' '
+	subj="$(echo "Subject: [other] message" |
+		git mailinfo -b /dev/null /dev/null)" &&
+	test z"$subj" = z"Subject: [other] message"
+'
+
+test_expect_success 'mailinfo -b leading [PATCH]' '
+	subj="$(echo "Subject: [PATCH] [other] message" |
+		git mailinfo -b /dev/null /dev/null)" &&
+	test z"$subj" = z"Subject: [other] message"
+'
+
+test_expect_success 'mailinfo -b double [PATCH]' '
+	subj="$(echo "Subject: [PATCH] [PATCH] message" |
+		git mailinfo -b /dev/null /dev/null)" &&
+	test z"$subj" = z"Subject: message"
+'
+
+test_expect_failure 'mailinfo -b trailing [PATCH]' '
+	subj="$(echo "Subject: [other] [PATCH] message" |
+		git mailinfo -b /dev/null /dev/null)" &&
+	test z"$subj" = z"Subject: [other] message"
+'
+
+test_expect_failure 'mailinfo -b separated double [PATCH]' '
+	subj="$(echo "Subject: [PATCH] [other] [PATCH] message" |
+		git mailinfo -b /dev/null /dev/null)" &&
+	test z"$subj" = z"Subject: [other] message"
+'
+
 test_done