pager: default to LESS=FRS

Recent change to paginate "git diff" by default is often irritating
when you do not have any change (or very small change) in your working
tree.
Signed-off-by: NJunio C Hamano <junkio@cox.net>

pager.c

@@ -50,7 +50,7 @@ void setup_pager(void)
 	close(fd[0]);
 	close(fd[1]);
 
-	setenv("LESS", "-RS", 0);
+	setenv("LESS", "FRS", 0);
 	run_pager(pager);
 	die("unable to execute pager '%s'", pager);
 	exit(255);