This is not a traditional song; it was written quite recently by Jack Foley, a Glasgow journalist and for some years editor of The Folksong Broadsheet.  The full text (which is still very much in copyright) can be seen at the  Tradition Bearers  website.  There is a sound sample of Bob Blair singing it there, too, but at present connections are poor and I can't get it to play, so I can't tell you whether or not Paddy Graber has changed the tune; he has only slightly altered Foley's text, and can only have learned it in recent years.