sparse-checkout: free string list after displaying

In sparse_checkout_list(), we put the hashmap entries into a string_list
so we can sort them. But after printing, we forget to free the list.

This patch drops 5 leaks from t1091.

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

Author: peff

builtin/sparse-checkout.c

@@ -95,6 +95,8 @@ static int sparse_checkout_list(int argc, const char **argv, const char *prefix)
 			quote_c_style(sl.items[i].string, NULL, stdout, 0);
 			printf("\n");
 		}
+
+		string_list_clear(&sl, 0);
 	} else {
 		write_patterns_to_file(stdout, &pl);
 	}