#...
require 'whenever/capistrano'
#...

set :whenever_command, "bundle exec whenever"

set :bundle_flags, "--deployment --quiet --binstubs"

set :default_environment, {
  'PATH' => "$HOME/.rbenv/shims:$HOME/.rbenv/bin:$PATH"
}

#...

namespace :rbenv do
  task :rehash do
    run 'rbenv rehash'
  end
end

task :backup do
  run "cd #{current_path} && bundle exec rake backup RAILS_ENV=#{rails_env}"
end

#...

after "bundle:install", "rbenv:rehash"