add script for scroll up testing

ptty.c

@@ -130,7 +130,7 @@ main(int argc, char *argv[])
 
 			/* handle cursor position request */
 			if (strcmp("\033[6n", buf) == 0) {
-				dprintf(mfd, "\033[%d;%dR", 1, 1);
+				dprintf(mfd, "\033[1;25R", 1, 1);
 				break;
 			}
 

up.sh

@@ -0,0 +1,8 @@
+#!/bin/sh
+
+set -eu
+
+jot 50 > tmp.log
+
+(sleep 1; printf "\033[5;2~"; sleep 1; ) \
+	| ktrace -i ./ptty ./scroll ksh -c "tail -fn 50 tmp.log" > out.log