t6050-replace: add test to clean up all the replace refs

Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t6050-replace.sh

@@ -276,4 +276,10 @@ test_expect_success '-f option bypasses the type check' '
 	git replace -f HEAD^ $BLOB
 '
 
+test_expect_success 'replace ref cleanup' '
+	test -n "$(git replace)" &&
+	git replace -d $(git replace) &&
+	test -z "$(git replace)"
+'
+
 test_done