When modern artists embrace her forgotten album “Just Another Diamond Day,” failed U.K. folk singer Vashti Bunyan experiences popularity like never before. This documentary profiles her disappointing career and astonishing resurgence 30 years later. Featuring interviews with Andrew Loog Oldham, Joe Boyd and Robert Kirby, this charming movie follows Bunyan as she takes a nostalgic road trip and prepares for the biggest concert of her life.