Doc: NR 4.2.2 layout-set-staff-size warning

[Federico Bruni]

Hi

In the Notation Reference, chapter 4.2.2, there's this warning:

layout-set-staff-size does not change the distance between the staff 
lines.

What does it mean with "distance between the staff lines"?
Isn't it the staff height? (as the distance between the staff lines is 
equal)

layout-set-staff-size does print the correct staff height, so I don't 
understand what this warning is about.
I'm missing something? Or documentation is not up-to-date?
I suspect the latter, since `git log --grep layout-set-staff-size` 
shows some comments which suggest it didn't use to work fine. For 
example:

commit b38989c86d64ef41025672f9bd2d2fcfd6cd700e
Author: David Kastrup <...>
Date: Thu Nov 13 23:29:10 2014 +0100

Issue 216/2: Adapt repeat-sign-* regtests
Since layout-set-staff-size now gets staffsize right, the regtests
should no longer compensate for bad staffsize.







Minimal example:

\version "2.19.82"

mus = \relative {
c'4. d8 e2
}

% Default is 20pt.
\score {
\new Staff \mus
\layout { }
}

% Explicit 20pt.
\score {
\new Staff \mus
\layout {
#(layout-set-staff-size 20)
}
}

% 14 pt
\score {
\new Staff \mus
\layout {
#(layout-set-staff-size 14)
}
}

% 25pt
\score {
\new Staff \mus
\layout {
#(layout-set-staff-size 25.2)
}
}