selective-display

selective-display is a variable defined in `C source code'.
Its value is

nil

• Automatically becomes buffer-local when set.

Documentation:
Non-nil enables selective display.
An integer N as value means display only lines
that start with less than N columns of space.
A value of t means that the character ^M makes itself and
all the rest of the line invisible; also, when saving the buffer
in a file, save the ^M as a newline.