A gypsy and the son of a general—impossible love. An uprising overthrown and the gypsy learning she’s of noble birth—happy ending. That’s the story of Paquita, a two-act ballet premiered in Paris in 1846, revised by Petipa in Russia in 1847, yet performed solely in bits and pieces in the 20th century. The Mariinsky has pulled choreography from period notation, tweaked the plot, and unveils its full-length Paquita at the Kennedy Center this month. —L.J.