I just posted The Black Nag on http://www.whistleandsqueak.com/folk_traditional_and_classical. I think I counted 16 octave changes. It is a very fun tune.
Enjoy!
This is a B minor setting of the English dance tune from Playford (1657), published originally in what seems to be D Major:
http://www.izaak.unh.edu/nhltmd/indexes/dancingmaster/Dance/Play0992.htm
Try keeping the bottom 1st finger (B1) down throughout the entire tune. This is a lazy fingering that can apply to the bottom scale half of many B minor tunes (Cock and Hen, Coleraine Jig, etc.).
Also, try playing it transposed in Am instead, for a good exercise to check if your cross-fingered C-natural is clean. 
Haste to the Wedding has a few A octave jumps.