The tune is The Valley of Knockanure. I should point out however, that Eoin Ó Dubhthaigh was a notorious fascist (note the reference to blueshirts, which was part of the National Guard uniform), who compared himself favourably to Hitler and Mussolini, and who led the Irish Brigade, which fought on the side of Franco.

I am surprise that Ronnie Drew of all people would want to sing a song about such a crud.