const char *set = diff_get_color_opt(o, DIFF_METAINFO);
const char *reset = diff_get_color_opt(o, DIFF_RESET);
+ /* Never use a non-valid filename anywhere if at all possible */
+ name_a = DIFF_FILE_VALID(one) ? name_a : name_b;
+ name_b = DIFF_FILE_VALID(two) ? name_b : name_a;
+
a_one = quote_two(o->a_prefix, name_a + (*name_a == '/'));
b_two = quote_two(o->b_prefix, name_b + (*name_b == '/'));
lbl[0] = DIFF_FILE_VALID(one) ? a_one : "/dev/null";