Jim Bainbridge, As far as this song by Tannahill is concerned, we are not talking about the tradition. Tannahill was a nineteenth centuary published poet. He wrote a poem which he set to the tune The Three Carles o' Buchannan. About ten years after he died his friend R A Smith set it to another tune, a well know traditional version of a dance tune called The Braes o' Balquhidder.
Burns was different in that if you read his letters and notes to his songs he makes it clear that he was mainly rescuing old tunes and fragments of verses. There was no question of claiming traditional material was his own ... quite the contrary.
The "folk traditional" as far as Tannahill's original lyrics is concerned is that travellers like Jeannie Roberston conflated a poem by Hugh McWilliams, another published nineteenth centuary poet, with Tannahill's hence the many hybrid versions which occur from works by two non traditional poets who were writing in the nineteenth centuary.
I am still looking for Muttley's/Les Wilson's version to help with the chords.