Putting this here so I'm not downloading and running an uncontrolled script as root all the time.

updateghost.sh

#!/bin/bash
# Written by Andy Boutte and David Balderston of howtoinstallghost.com, ghostforbeginners.com and allaboutghost.com
# updateghost.sh will update your current ghost install to the latest version without you losing any content

if [ -f config.js ]
	then
	echo `whoami`
	# Make temporary directory and download latest Ghost.
	mkdir temp
	cd temp
	curl -L -O https://ghost.org/zip/ghost-latest.zip
	unzip *.zip
	cd ..

	# Make database backups.
	for file in content/data/*.db;
		do cp "$file" "${file}-backup-`date +%Y%m%d`";
	done

	# Copy the new files over.
	yes | cp temp/*.md temp/*.js temp/*.json .
	rm -R core
	yes | cp -R temp/core .
	yes | cp -R temp/content/themes/casper content/themes
	npm install --production

	# Delete temp folder.
	rm -R temp

	echo "You can now start Ghost with npm, forever or whatever else you use."
else
	echo "Please cd to your Ghost directory."

fi