Change to \rest markup in 2.23

[David F.]

In 2.23, the rest markup command changed from taking a string to taking a 
duration.

\version "2.22"
\markup \rest #"4.."

\version "2.23"
\markup \rest { 4.. }

It would be nice if this change were backward compatible, at least for a 
version or two.

My primary Lilypond environment is v2.22.2-1 on macOS 10.14.  This is the 
environment I use for final “production” of scores.  But I’ve been trying to do 
as much development as possible in v2.23 on macOS 10.15.

Unfortunately, the change to the rest markup command makes going back and forth 
quite cumbersome.  Would be be possible to make this command take either a 
string or duration?

David F.