added debugging set-x.tape

src/tests/vhs/set-x.tape

@@ -0,0 +1,57 @@
+# Where should we write the GIF?
+Output ./../media/terminal/set-x.gif
+
+# Set up a 1200x600 terminal with 46px font.
+Set Margin 0
+Set FontSize 19
+Set Width  600
+Set Height 500
+Set CursorBlink true
+
+# Type a command in the terminal.
+Type 'vi'
+
+# Pause for dramatic effect...
+Sleep 1000ms
+
+Enter
+
+# Type a command in the terminal.
+Type "i#!/bin/sh"
+
+Enter
+
+Type "set -x   # enable debugging
+Enter
+Enter
+Type "foo=bar"
+Enter
+Type "echo $foo"
+Enter
+
+Sleep 4000ms
+
+# Type a command in the terminal.
+Escape
+Type ":wq! myscript"
+
+# Pause for dramatic effect...
+Sleep 2000ms
+
+Enter
+
+Type "chmod +x myscript"
+
+Sleep 1000ms
+
+Enter
+
+Type "./myscript"
+
+Sleep 2000ms
+
+Enter 
+
+# Admire the output for a bit.
+Sleep 4s
+