I mistyped when I asked this question regarding RTClib. That would be quite a trick
I need to rename a file on SD card after it is detected and used to configure the device. I see no way to directly rename a file. Perhaps copy to a new name and delete the old one, but I see nothing to use to copy either. Two files open at once for a byte by byte copy seems like a bad idea.
You can read more than one byte at a time. Given that SdFat is not a full-blown file system, copy and delete seems to be the only way to accomplish what you want to do.
Excellent. If you make a function out of it, it becomes re-usable. You might even post the function here, for others that want to do something similar.