Mine update for https://aur.archlinux.org/packages/lightdm-pantheon-greeter-bzr

lightdm-pantheon-greeter.install

whisperer(){
	echo "----------------------------------------------------------------"
	echo "Set these settings in '/etc/lightdm/lightdm.conf':"
	echo "  greeter-session=pantheon-greeter"
	echo "  greeter-user=root"
	echo ""
	echo "For changing background use a GSettings editor while in root"
	echo "and navigate into path: org.pantheon.desktop.greeter"
	echo ""
	echo "You might want to read:"
	echo "https://wiki.archlinux.org/index.php/LightDM#Changing_your_avatar"
	echo "----------------------------------------------------------------"
}

post_install() {
	mkdir -p /usr/share/backgrounds
	glib-compile-schemas usr/share/glib-2.0/schemas
	whisperer
}

post_remove() {
	glib-compile-schemas usr/share/glib-2.0/schemas
}


post_update(){
	mkdir -p /usr/share/backgrounds
	whisperer
}

PKGBUILD-bzr

# Maintainer: Maxime Gauduin <alucryd@gmail.com>
# Contributors: M0Rf30, faidoc, sh4nks, PedroHLC

pkgname=lightdm-pantheon-greeter-bzr
pkgver=r274
pkgrel=0

pkgdesc="LightDM greeter from the ElementaryOS team written in Vala "
arch=('i686' 'x86_64')
url="https://launchpad.net/pantheon-greeter"
license=('GPL')
groups=('lightdm')
depends=('granite' 'libindicator-gtk3' 'clutter-gtk' 'lightdm' 'gdk-pixbuf2' 'gnome-settings-daemon')
optdepends=('onboard: Onscreen Keyboard'
	'indicator-sound: Sound Indicator'
	'indicator-power: Power Indicator'
	'numlockx: Automatically sets numlock'
	'gtk-theme-elementary-bzr: Default theme'
	'gnome-themes-standard: High-Contrast theme'
	'elementary-icon-theme-bzr: Default icon theme'
	'ttf-droid: Installs Droid Sans, the default font family'
	'dconf: To change settings')
makedepends=('cmake' 'vala' 'bzr')
provides=('pantheon-greeter')

install=lightdm-pantheon-greeter.install
source=("bzr+lp:pantheon-greeter")
md5sums=('SKIP')

build(){
  cd "$srcdir"/pantheon-greeter/
  [ -d build ] && rm -rf build
  mkdir build
  cd build
  CFLAGS="$CFLAGS -lm -Wno-deprecated-declarations"
  cmake .. -DCMAKE_INSTALL_PREFIX=/usr
  make ${MAKEFLAGS}
}

package(){
	cd "$srcdir"/pantheon-greeter/build/
	make DESTDIR="${pkgdir}" install
}