warn on low battery

Addresses part of #18

roles/laptop/files/lowbatt.sh

@@ -0,0 +1,15 @@
+#!/bin/sh
+
+capacity='low'
+
+# Try to get an actual percentage.
+if [ -f /sys/class/power_supply/BAT0/capacity ]; then
+    capacity="at `cat /sys/class/power_supply/BAT0/capacity`%"
+fi
+
+# Build the message body.
+message="Battery is $capacity. We need more power, Scotty!"
+
+# Make some noise.
+notify-send --urgency=critical "Low Battery" "$message"
+wall "Battery is low. $message"

roles/laptop/files/udev.rules

@@ -1 +1,2 @@
+SUBSYSTEM=="power_supply", ATTR{status}=="Discharging", ATTR{capacity}=="[5-10]", RUN+="/usr/local/bin/lowbatt.sh"
 SUBSYSTEM=="power_supply", ATTR{status}=="Discharging", ATTR{capacity}=="[0-5]", RUN+="/usr/bin/systemctl suspend"

roles/laptop/tasks/main.yml

@@ -5,5 +5,8 @@
 - name: Copy logind configuration file
   copy: src=logind.conf dest=/etc/systemd/logind.conf
 
-- name: Push udev rule to suspend on low battery
+- name: Push low battery warning script
+  copy: src=lowbatt.sh dest=/usr/local/bin/lowbatt mode=0755
+
+- name: Push low battery udev rules
   copy: src=udev.rules dest=/etc/udev/rules.d/99-lowbat.rules