Add custom "Copy as" submenu

Question

I would like to add another command to "Save as" menu that is generated by right clicking on selected text.

We have there "Plain Text" and after this I would like to add "Sagemath code". After clicking on it the text/code would be copied as plaintext with addition that spaces that represent multiplication would be replaced with "*".

For example if you "copy as plain text" this code 3 x^2 + 2 x + 1 you get string "3 x^2 + 2 x + 1" but I would like it to be 3*x^2 + 2*x + 1 because Sagemath recognizes only "*" as multiplication.

Sorry no code from me. I have no clues how to do it.

Update:

Why the code from here does not work anymore?

The code should rewrite the file MenuSetup.tr with new menu (in my code with unchanged default menu) but when I look at the file its modification time is not changed which means nothing was done to the file Wolfram Research\Mathematica\8.0\SystemFiles\FrontEnd\TextResources\Windows\MenuSetup.tr.

Begin["System`"];
menu = Get[
   FileNameJoin[{$InstallationDirectory, "SystemFiles", "FrontEnd", 
     "TextResources", "Windows", "MenuSetup.tr"}]];
End[];
FrontEndExecute[FrontEnd`ResetMenusPacket[menu]]

Answer 1

In fact it is the file ContextMenus.tr that has to be modified. I did it manually in text editor.

In the "Input" -> { section of the file I added:

MenuItem["SageMath", FrontEndExecute[{FrontEnd`NotebookApply[FrontEnd`InputNotebook[],"InputForm[\[SelectionPlaceholder]]",All],FrontEndToken["Evaluate"]}]]

It applies InputForm to selected code.

I was unable to figure out how to also copy it to clipboard.

If someone see a way to add copy to clipboard after applying InputForm or even better leave the selected code untouched just copy it to clipboard in "input form" I would be happy to see it.