Enable detect by default for the moment.

main.ml

@@ -46,6 +46,7 @@ let setup_logs =
 (* Commands. *)
 
 let config cmd detect filename () =
+  let filename = Option.value filename ~default:Solver.default_config_filename in
   Logs.debug
     (fun m -> m "Command `%s' with configuration file `%s'."
         cmd filename);
@@ -87,7 +88,7 @@ let config_cmd =
     let doc =
       Format.sprintf "$(b,FILE) to write the %s configuration to." caisar
     in
-    Arg.(value & pos 0 file Solver.default_config_filename
+    Arg.(value & pos 0 (some string) None
          & info [] ~docv:docv_filename ~doc)
   in
   let doc = Format.sprintf "%s configuration." caisar in
@@ -104,9 +105,11 @@ let config_cmd =
   in
   Term.(ret
           (const (fun cmdname detect filename _ ->
-               if not detect
+               if not detect && Option.is_none filename
                then `Help (`Pager, Some "config")
-               else `Ok (config cmdname detect filename ()))
+               else
+                 (* TODO: Do not enable [detect] by default. *)
+                 `Ok (config cmdname true filename ()))
            $ const cmdname $ detect $ filename $ setup_logs)),
   Term.info cmdname ~sdocs:Manpage.s_common_options ~envs ~exits ~doc ~man