The tune isn't really 'Willie O'Winsbury' at all, though nowadays everybody thinks it is. What happened was that Andy Irvine accidentally copied out the wrong tune from the appendix to Child's English and Scottish Popular Ballads; it was 'Fause Foodrage', not 'Willie' (which was on the next page and completely different). He didn't realise his mistake, apparently, until after Anne Briggs had recorded it.
The DT file can easily be found by running a search here for farewell farewell today, just as it could be when the original question was asked six years ago.
If these are accurate (and of course the site wasn't there when this old thread was new), then my hearing "ever swear" was wrong; but it's "loathe", not "love".
Howie didn't need the lyric, but wanted to know what it meant. I recall somebody from Fairport saying, a while after Richard had left the band, that he had never told them what any of his songs meant. This would be a case for making up a "meaning" that has some significance to you if you need one; but keeping it to yourself. You're unlikely to get one from the horse's mouth, far less from any of us.