--- /dev/null
+@node Options
+@section Options
+
+There few configuration options taken from @file{cmd/env.rc}. You can
+override them either with environment variables, or by editing that file
+directly. You can override @command{curl}, @command{wget},
+@command{zstd}, @command{parallel} command invocations,
+@code{User-Agent}, number of download/parse jobs run in parallel and so on.