Use different rails log for rake tasks

logging.rake

# Use like:    `task mytask: :setup_logger do`
# Rather than: `task mytask: :environment do`
task setup_logger: :environment do
  set_logger(file: Rails.root.join('log', 'rake.log'))
end

# Or just call set_logger(file: 'custom_file.log') from your rake task. Be sure to use an absolute path.
def set_logger(file: STDOUT, level: Logger::INFO)
  logger           = ActiveSupport::TaggedLogging.new(Logger.new(file))
  logger.level     = level
  logger.formatter = Rails.logger.formatter
  Rails.logger     = logger
end

# Technically, it's better to just log to STDOUT 12-factor style. 
# Change ActiveRecord::Base.logger to change where the queries are logged.