variable_based_ruby_version_override_in_capistrano.rb

deploy.rb

set :rvm_ruby_version do
  fetch(:override_rvm_ruby_version, IO.read('.ruby-version').strip)
end

after 'deploy:updating', 'custom:tweak_ruby_version' do
  ruby_version = fetch(:override_rvm_ruby_version, nil)
  next unless ruby_version
  on roles :all do
    info "Overwriting .ruby-version with #{ruby_version.inspect}"
    content = StringIO.new(ruby_version)
    upload! content, File.join(fetch(:release_path), '.ruby-version')
  end
end

vagrant.rb

set :override_rvm_ruby_version, 'jruby-9.2.4.0'