Seen it called all three.. First heard it on the streets of Dublin.. it really made a powerful impression. Learned it as GFF. This will probably always be it's name in my psyche. I generally squeak it by in "G" though "F" would probably work better.... but the chords are so easy in "G!"

Ah Well.. the 12-string is usually tuned down a couple frets - but I mostly play the 6 nowadays...

Fantastic song any way you call it..

Cheers, BK