dh_installwm is a debhelper program that is responsible for generating the postinst and postrm commands that register a window manager with update-alternatives(8)
Any window manager programs specified as parameters will be registered in the first package dh_installwm is told to act on. By default, this is the first binary package in debian/control, but if you use -p, -i, or -a flags, it will be the first package specified by those flags.
Set the priority of the window manager. Default is 20, which is too low for most window managers; see the Debian Policy document for instructions on calculating the correct value.
Do not modify postinst/postrm scripts. Turns this command into a no-op.