Logger does not support "truncate" options and truncates output always.

[deemytch]

config :logger, :dev_log,
  path: "/tmp/dev.log",
  level: :debug,
  format: "$date\t$time\t$level\t●$message●$metadata\n",
  truncate: :infinity

Still truncates long output with "(truncate)" at end

[DohanKim]

+1