Ruby setup.rb with singleton extension

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Ruby

Actual i'm experimenting with Rubys setup.rb [^].

I have defined a hook file like:

# post-install.rb
require 'fileutils'

prefix = "#{Dir.home}/.rvm/rubies/default"
datadir = "#{prefix}/share"
desktopfile = "#{Dir.home}/.local/applications/latex_curriculum_vitae.desktop"

FileUtils.touch(desktopfile)
File.write "#{desktopfile}", <<EOF
[Desktop Entry]
Version=1.0
Type=Application
Name=Job-Application Creator
Exec=latexcv.rb
Icon="#{datadir}/latex_curriculum_vitae/Pictures/arbeitsagentur.png"
EOF

The Release Note for the latest ruby.rb says: Hook API is no longer supported ; support is now handled via singleton extension.

But it is sadly not well documented.

Maybe anyone can share experience?