Swallowtail Jig is a classic Irish & American session tune.
This is an exceptionally common tune – for this reason, there are *lots* of slightly (or drastically) different versions. This is mine.
If your version of the melody is a few notes different, it will probably work OK with this one – as long as everyone keeps good time.
If your version of the chords is different, it may or may not work OK with this one. Best to ask.