upgrade.rb

#!/bin/env ruby
require 'fileutils'

DRUPAL_MAJOR = 6

puts "Scanning for available drupal versions"

available = Dir['*'].map do |file|
  if file =~ /^drupal-#{DRUPAL_MAJOR}\.(\d+)$/
    $1.to_i
  end
end.compact

if available.empty?
  puts "Not a drupals directory"
  exit 1
end

puts "Found: 6.#{available.map{|c| c.to_s}.join(", 6.")}"

candidate = available.max

puts "Upgrade candidate: #{DRUPAL_MAJOR}.#{candidate}"
puts "Detecting current version"

if File.symlink?('drupal-stable/index.php') &&
   File.readlink('drupal-stable/index.php') =~ /drupal-#{DRUPAL_MAJOR}.(\d+)/
  current = $1.to_i
else
  puts "Cannot identify current installation"
  exit 2
end

puts "Current version is #{DRUPAL_MAJOR}.#{current}"

if candidate <= current
  puts "No upgrade needed"
  exit 3
end

relink = %w{cron.php includes index.php install.php misc modules profiles scripts themes update.php xmlrpc.php}
cur_dir = "./drupal-stable"
new_dir = "../drupal-#{DRUPAL_MAJOR}.#{candidate}"
puts "Relinking"
relink.each do |item|
  cur_file, new_file = "#{cur_dir}/#{item}", "#{new_dir}/#{item}"
  puts "  #{cur_file} -> #{new_file}"
  File.unlink cur_file
  File.symlink new_file, cur_file
end