Have you noticed how some people sing it "I've been working all day" and some people "I've been walking all day" - I'm pretty sure Eric Bogle wrorte it as "walking" -but the way Irish singers pronounce makes it sound like it might be "working". And then others learn it fronm the singing, and sing it as "working".

That's the folk process. I think "working" is actually better, in a way - it suggests someone who's come across the grave by chance, when he's doing a days work, maybe on a building site somewhere, rather than a tourist who's come to see the war graves.

Once a song is on the loose, it takes on a life of its own, regardless of the wishes of the person who made it up. The same way, though I know Eric Bogle wrote it as "No Man's Land" and prefers that title, it's almost always called "Willie McBride" or "The Green Fields of France".