It is the first one
The language of technical reports
a. Wild celebration
A revel is a wild celebration. Your context clue here is the detail that it went "whirlingly on". This gives the image that things are spinning and it is something that could end at midnight. An party hat doesn't end at midnight. A type of dance is something that can spin, but it usually doesn't continue on until midnight. A specific dance type usually only last for a few minutes. An appearance does not make sense.
One similarity is they both make wonderful pets. A huge difference is a Maltese has no undercoat and is described as a white fluff ball and a German Shepherd is multicolored coming in white, black, brown. The Maltese is a tiny breed while German Shepherds are big and strong
