simple capistrano multistage

deploy.rb

# put this in deploy.rb, set proper values and remove all "set" and "role" calls that are here from the global namespace

desc "Run tasks in staging enviroment."                                                                                                                                                        
task :staging do                                                                                                                                                                               
  set :keep_releases, 3                                                                                                                                                                        
  set :rvm_ruby_string, 'ruby-1.9.3-p0-falcon'                                                                                                                                                 
  set :deploy_to,  "/home/deploy/#{application}"                                                                                                                                               
  role :app, application                                                                                                                                                                       
  role :web, application                                                                                                                                                                       
  role :db, application, :primary => true                                                                                                                                                      
  set :branch do                                                                                                                                                                               
    current_branch = %x[ git branch | grep ^* | awk {'print $2'} ].chomp                                                                                                                       
                                                                                                                                                                                               
    branch = Capistrano::CLI.ui.ask "Branch to deploy (make sure to push the branch first): [#{current_branch}] "                                                                              
    branch = current_branch if branch.empty?                                                                                                                                                   
    branch                                                                                                                                                                                     
  end                                                                                                                                                                                          
end

desc "Run tasks in production enviroment."                                                                                                                                                     
task :production do                                                                                                                                                                            
  # Prompt to make really sure we want to deploy into prouction                                                                                                                                
  puts "\n\e[0;31m Are you REALLY sure you want to deploy to production?"                                                                                                                      
  print " Enter y/N + enter to continue: "                                                                                                                                                     
  proceed = STDIN.gets[0..0] rescue nil                                                                                                                                                        
  exit(1) unless proceed == 'y' || proceed == 'Y'                                                                                                                                              
                                                                                                                                                                                               
  puts "\e[0m\n"                                                                                                                                                                               
                                                                                                                                                                                               
  # set production specific things                                                                                                                                                             
  set :keep_releases, 30                                                                                                                                                                       
  set :rvm_ruby_string, 'default'                                                                                                                                                              
  set :deploy_to,  "/home/deploy/app_name"                                                                                                                                              
  role :app, 'app_name'                                                                                                                                                                 
  role :web, 'app_name'                                                                                                                                                                 
  role :db, 'app_name', primary: true                                                                                                                                                   
  set :branch do                                                                                                                                                                               
    default_branch = 'stable'                                                                                                                                                                  
                                                                                                                                                                                               
    branch = Capistrano::CLI.ui.ask "Branch to deploy (make sure to push the branch first): [#{default_branch}] "                                                                              
    branch = default_branch if branch.empty?                                                                                                                                                   
    branch                                                                                                                                                                                     
  end                                                                                                                                                                                          
end