deploy.rb

set :asset_precompile_locations, ["config/application.rb", "app/assets"] # We check the git log for these locations to determine if recompilation necessary

# ...

  namespace :assets do

    task :recompile, :roles => :web do
      run %Q{cd #{latest_release} && #{rake} RAILS_ENV=#{rails_env} GROUP=assets assets:precompile}
    end

    task :symlink do
      run "ln -s #{shared_path}/assets #{latest_release}/public/assets"
    end

    task :precompile, :roles => :web, :except => { :no_release => true } do
      needs_recompile = if current_revision
        from = source.next_revision(current_revision)
        capture("cd #{latest_release} && #{source.local.log(from)} #{asset_precompile_locations.join(' ')} | wc -l").to_i > 0
      end

      # Symlink public/assets to the shared assets directory.
      symlink

      if needs_recompile
        recompile
      else
        logger.info "Skipping asset pre-compilation because there were no asset changes"
      end
    end
  end