Setting page size from the command line

[Cameron Horsburgh]

Hi folks,

I'm in the process of writing up some of the previously undocumented
features in the NEWS files. I'm having a bit of trouble with this comment:

**********
The default paper size may now be set from the command line using
-dpaper-size.
**********

I'm having trouble passing paper sizes to it. I've tried these:

lilypond -dletter sample.ly
lilypond -da5 sample.ly
lilypond -dA5 sample.ly
lilypond -da3 sample.ly

In all cases I get the default a4 output and a warning:

warning: no such internal option: letter (a5 or whtever it was.)

After looking at the usage statement I tried

lilypond -dpaper-size=a5 sample.ly

but I get:

ERROR: Unbound variable: a5

I've played around with a few other possibilities, with no good result.
Can somebody tell me how this option is supposed to be called? Thanks in
advance,

Cameron