Renaming files on the SD card

This is unfortunate. Does anybody know when an updated IDE-standard SD library will exist with a rename feature?

Does anybody know the equivalent of this SD code using SdFat?

//if logfile.txt doesn't exist, SD.open creates a new file, if it exists, it appends data to it
  File dataFile = SD.open("logfile.txt", FILE_WRITE);  
  if (dataFile) {    // If the file is available, write to it
    dataFile.println("Hello");
    dataFile.close();
    }

How do I create this same functionality from SdFat?

Also, what is the equivalent of,

if (SD.exists("now.csv"))

?