code: protected boolean wouldProduceSameFile (String generated, File existing)
          throws IOException
      {
          Iterator<String> generatedLines = Splitter.on(EOL).split(generated).iterator();
          for (String prev : Files.readLines(existing, UTF_8)) {
              if (!generatedLines.hasNext()) {
                  return false;
              }
              String cur = generatedLines.next();
              if (!prev.equals(cur) && !(prev.startsWith("// $Id") && cur.startsWith("// $Id"))) {
                  return false;
              }
          }
  
          // If the generated output ends with a newline, it'll have one more next from the splitter
          // that reading the file doesn't produce.
          if (generatedLines.hasNext()) {
              return generatedLines.next().equals("") && !generatedLines.hasNext();
          }
          return true;
      }
docs: Returns true if the given string has the same content as the file, sans svn prop lines.