I now have a change set that makes PseudoClass pick up a class comment/
definition from the image when there isn't one in the file, depending
on a new preference fileContentsBrowserShowsSystemInfo,

BUT this is the first change set I've needed to make where one of the
changes is an action (Preferences addPreference: ...) and that change
did not make it into the change set.

How do I get an initialisation action like creating a new Preference
into a change set?