Vendor the external cookbooks

Knife-Zero doesn't include Berkshelf support, so vendoring everything in
the repo is convenient again

cookbooks/users/libraries/osx_helper.rb

@@ -0,0 +1,29 @@
+module Users
+  # Helpers for Users
+  module OsxHelper
+    def dscl(*args)
+      host = '.'
+      stdout_result = ''
+      stderr_result = ''
+      cmd = "dscl #{host} -#{args.join(' ')}"
+      status = shell_out(cmd)
+      status.stdout.each_line { |line| stdout_result << line }
+      status.stderr.each_line { |line| stderr_result << line }
+      [cmd, status, stdout_result, stderr_result]
+    end
+
+    def safe_dscl(*args)
+      result = dscl(*args)
+      return '' if (args.first =~ /^delete/) && (result[1].exitstatus != 0)
+      raise(Chef::Exceptions::Group, "dscl error: #{result.inspect}") unless result[1].exitstatus == 0
+      raise(Chef::Exceptions::Group, "dscl error: #{result.inspect}") if result[2] =~ /No such key: /
+      result[2]
+    end
+
+    def gid_used?(gid)
+      return false unless gid
+      groups_gids = safe_dscl('list /Groups gid')
+      !!(groups_gids =~ Regexp.new("#{Regexp.escape(gid.to_s)}\n"))
+    end
+  end
+end