ManToGif code: how can I avoid time-reversal in the animated GIF? [duplicate]

Question

ManToGif is a very useful function to create smooth animated GIF from aManipulate expression.

ManToGif[man_, name_String, step_Integer] := 
  Export[
   name <> ".gif", 
   Import[
     Export[
       name <> 
         Which[
           $OperatingSystem == "MacOSX", ".mov", 
           $OperatingSystem == "Windows", ".avi"], 
        man], 
     "ImageList"][[1 ;; -1 ;; step]]];

The created animated GIF runs forward and them runs backward.

Unfortunately, I don't understand details of ManToGif, so I don't know how to create a GIF that only runs forward. Do you know how to specify it?