Based on an old English balled, the song became a standard among folk-blues and traditional jazz musicians.
regular gCEA (should also work in low G)
Even though this is tabbed in straight eights, the feel is a slow blues shuffle. It is a wonderful basis for improvisation. I wrote down the main eight-bar theme as I remember it and just two variations that came to my mind while working on the tab.
In the second part I added some harmonics (the notes in boxes) and played around with some triplets. In the end of the third part I changed one chord (red). Fingered it accidentally, and liked it. This tune can be altered endlessly.