update your itunes liberry

update-itunes.rb.js

require 'osx/cocoa'
require 'optparse'
include OSX
OSX.require_framework 'ScriptingBridge'

iTunes = SBApplication.applicationWithBundleIdentifier_('com.apple.iTunes')

$opts = {}
optparse = OptionParser.new do |args|
    args.banner = 'Usage: update-itunes.rb [opts] <path>'
    args.on('-v', '--[no-]verbose', 'Run verbosely') do |v|
        $opts[:verbose] = v
    end
end.parse!

if ARGV.empty?
    puts 'Error: must specify directory'
    exit(-1)
else
    $opts[:path] = ARGV[0]
end

def deleteTrack(track)
    puts "Deleting missing song #{track.name} from library" if $opts[:verbose]
    track.delete
end

cur_songs = []
iTunes.sources[0].libraryPlaylists[0].fileTracks.get.each do |track|
    deleteTrack(track) if track.location == nil
    if track.location != nil
        if not File.exists?(track.location.path)
            deleteTrack(track)
        else
            cur_songs.push(track.location.path)
        end
    end
end

Dir.glob($opts[:path] + '/**/*.mp3').each do |file|
    if not cur_songs.include? file
        puts "Adding new track #{file} to library" if $opts[:verbose]
        track = NSArray.arrayWithArray([NSURL.fileURLWithPath(file)])
        iTunes.add_to(track, nil)
    end
end