config.ru

rack_opts = {
  :precompilation_enabled => true
}

case ENV["DEPLOY_APPID"]
when "app-production", "app-staging", "app-test01", "app-test02"
  ver = ENV["DEPLOY_VERSION"]
  raise "DEPLOY_VERSION is blank" if ver.nil? || ver.empty?
  rack_opts[:application] = ENV["DEPLOY_APPID"]
  rack_opts[:version    ] = ver
when nil
  case ENV['USER']
  when "takeru"
    rack_opts[:application] = 'app-takeru'
    rack_opts[:version    ] = '001'
  when "john"
    rack_opts[:application] = 'app-john'
    rack_opts[:version    ] = '002'
  else
    # raise "unknown ENV['USER']=#{ENV['USER']}"
    # It's GAE Runtime..
  end
else
  raise "unknown DEPLOY_APPID=#{ENV['DEPLOY_APPID']}"
end
AppEngine::Rack.configure_app(rack_opts)

...

deploy.rb

#!/usr/bin/env ruby

unless File.exist?("Gemfile") && File.exist?("config.ru")
  puts "Gemfile or config.ru is not exist. #{Dir.pwd}"
  exit
end
app_id  = ARGV[0]
app_ver = ARGV[1]
if app_id.nil? || app_ver.nil?
  puts "usage: ruby script/deploy.rb APPID VERSION"
  exit
end
system("rm -f WEB-INF/appengine-web.xml; DEPLOY_APPID=#{app_id} DEPLOY_VERSION=#{app_ver} appcfg.rb update .")