trackball not working after sid upgrade

[Zenaan Harkness <zen@freedbms.net>]

OK, previously, I added to /usr/share/X11/xorg.conf.d/10-evdev.conf
the following lines which make the Logitech Trackman Marble work
beautifully (left small button gives scrolling function not
backward/forward for browser tab history, and right small button gives
middle button; perfect :) :

Section "InputClass"
        Identifier  "Marble Mouse"
        MatchProduct "Logitech USB Trackball"
        MatchIsPointer "on"
        MatchDevicePath "/dev/input/event*"
        Driver "evdev"
        Option "ButtonMapping" "1 8 3 4 5 6 7 2 2"
        Option "EmulateWheel" "true"
        Option "EmulateWheelButton" "8"
        Option "ZAxisMapping" "4 5"
        Option "XAxisMapping" "6 7"
        Option "Emulate3Buttons" "true"
EndSection


Now my recent sid upgrade (had not upgraded for about 2 months I
think) has evidently overwritten this.

So, do I just create my own .../xorg.conf.d file, to protect against upgrades?

TIA
Zenaan