command-line: 'lilypond -o', outputting to a directory

[Heikki Johannes Junes]

I was planning to put in Emacs mode Command on Region/Buffer to write
files to a temporary directory. Meanwhile, I found the following
obscurity:

One can use

   ly2dvi -o /tmp/ file.ly

and get

   /tmp/file.dvi

But one cannot use

   lilypond -o /tmp/ file.ly

So, it would be good, if one could specify the outputting directory with
'-o' option.

Greetings,

  Heikki