anchor.diff:  
   file_ref
       : 'fileRef' '=' REFERENCE ';'
  -    | 'productRef' '=' REFERENCE ';'
  +    ;
  +
  +product_ref
  +    : 'productRef' '=' REFERENCE ';'
       ;
   
   container_portal
  
positive.code: pbx_build_file
      : REFERENCE '=' '{'
          isa_pbx_build_file
          file_ref
          settings?
        '}' ';'
      ;
  
negative.code: 
  uses_tabs
      : 'usesTabs' '=' NUMBER ';'
      ;
  
  platform_filter
      : 'platformFilter' '=' (QUOTED_STRING|NON_QUOTED_STRING) ';'
      ;
  
  children
  