git-fsck-objects: Free tree entries after use

The Massif tool of Valgrind revealed that parsed tree entries occupy
more than 60% of memory allocated by git-fsck-objects.  These entries
can be freed immediately after use, which significantly decreases
memory consumption.

Signed-off-by: Sergey Vlasov <vsu@altlinux.ru>
Signed-off-by: Junio C Hamano <junkio@cox.net>

fsck-objects.c

@@ -184,10 +184,17 @@ static int fsck_tree(struct tree *item)
 			default:
 				break;
 			}
+			free(last->name);
+			free(last);
 		}
 
 		last = entry;
 	}
+	if (last) {
+		free(last->name);
+		free(last);
+	}
+	item->entries = NULL;
 
 	retval = 0;
 	if (has_full_path) {