Tags files and directories per Brett Terpstra's approach.

gistfile1.rb

#!/usr/bin/env ruby

def package?(file)
	results = `mdls -name kMDItemContentTypeTree "#{file}" | grep com.apple.package`
	results.length > 0
end

base = ARGV[0]
if !base
	script = File.basename("#{__FILE__}")
	puts "Usage: #{script} <base tag>"
	puts "#{script} \"#work\""
	puts "#{script} \"#play,:toplevel\""
	exit
end
base += ',' if !base.include?(':')

packages = []
tags = {}
Dir.glob('**/*') do |file|
	parts = file.split('/')
	if parts.length == 1
		parent_dir = ""
	else
		parent_dir = parts[0..-2].join('/')
	end
	if File.directory?(file)
		if (package?(file)) 
			packages << "#{file}/"
			full_tag = tags[parent_dir] || base
			`tag -s "#{full_tag}" "#{file}"`
		else
			if !packages.find { |pkg| file.start_with?(pkg) }
				file_tag = parts[-1].downcase.gsub(/[^a-zA-Z0-9\-]*/,'')
				full_tag = base
				if parent_dir.length() > 0
					full_tag = "#{tags[parent_dir]}:#{file_tag}"
				else
					full_tag = "#{base}:#{file_tag}"
				end
				tags[file] = full_tag

				`tag -s "@#{file_tag}" "#{file}"`
			end
		end
	else
		if !packages.find { |pkg| file.start_with?(pkg) }
			full_tag = tags[parent_dir] || base
			`tag -s "#{full_tag}" "#{file}"`
		end
	end
end