Pseudo-shell with Rails application.rb and environment.rb already loaded--like spork but no DRB and speeds up rake commands and rails console in addition to tests

jumpstart.rb

#!/usr/bin/env ruby

require 'benchmark'

if ARGV[0]
  ENV['RAILS_ENV'] = %w{development test production staging}.find { |e| e[0] == ARGV[0][0] } || ARGV[0]
else
  ENV['RAILS_ENV'] ='test'
end

load_time = Benchmark.realtime do
  print "Loading application.rb..."
  require File.expand_path('./config/application', Dir.pwd)

  # we'll use class reloading
  # thanks to spork for lots of direction here
  # https://github.com/sporkrb/spork-rails/blob/master/lib/spork/app_framework/rails.rb
  # https://github.com/sporkrb/spork-rails/blob/master/lib/spork/ext/rails-reloader.rb
  Rails::Engine.class_eval do
    def eager_load!
      railties.all(&:eager_load!) if defined?(railties)
      # but don't eager load the eager_load_paths
    end
  end
  print "and environment.rb..."
  require File.expand_path('./config/environment', Dir.pwd)
  ActiveSupport::Dependencies.mechanism = :load

  if Rails.env.test?
    print "and cucumber..."
    require 'rspec'
    begin
      require 'cucumber' # saves 0.4 seconds when running cucumber

      # this shaves off another 2 seconds
      # even though most of the loads technically fail
      ENV['RAILS_ROOT'] = Dir.pwd
      other_paths = File.read(Dir.pwd + "/features/support/env.rb").scan(/require ['"](.+?)['"]/).flatten
      other_paths.each do |path|
        print "and #{path}..."
        begin
          load(path + '.rb', true)
        rescue
        end
      end
    rescue LoadError
    end
  end

  print "and rake..."
  require 'rake'
end

puts "took %.2f seconds." % load_time

require 'readline'

# thanks to http://bogojoker.com/readline/
# and to https://github.com/ruby/ruby/blob/trunk/ext/readline/readline.c
AUTOCOMPLETE_COMMANDS = ['rake ', 'cucumber features/', 'rails ', 'rspec spec/'].sort
RAKE_COMMANDS = ['db', 'db:migrate', 'db:test:prepare', 'db:rollback', 'routes', 'sunspot:reindex', 'sunspot:solr:start', 'sunspot:solr:start', 'sunspot:solr:stop', 'assets:clean', 'assets:precompile']
Readline.completion_append_character = "" # space doesn't work on OS X :(
Readline.completion_proc = Proc.new do |str|
  command_candidates = AUTOCOMPLETE_COMMANDS.grep(/^#{Regexp.escape(str)}/)
  file_candidates = Dir[str+'*'].grep(/^#{Regexp.escape(str)}/)
  file_candidates.map! do |path|
    # add a space unless a directory
    File.directory?(path) ? path : path + ' '
  end
  rake_task_candidates = RAKE_COMMANDS.grep(/^#{Regexp.escape(str)}/)
  command_candidates + file_candidates + rake_task_candidates
end

history_file_path = ".jumpstart_history-#{Rails.env}"

# load old history
if File.exists?(history_file_path)
  Readline::HISTORY.clear
  File.read(history_file_path).lines.each { |l| Readline::HISTORY << l.chomp }
end

while line = Readline.readline("\033[1;30m#{Dir.pwd.sub(/.*\//, '')} \033[0;35m#{Rails.env} \033[0;34m$ \033[0m", true)
  if line.blank?
    Readline::HISTORY.pop # don't store blank commands in history
    next
  end
  given_command, *arguments = line.split

  command = (given_command == 'rails') ? './script/rails' : given_command

  unless given_command == 'eval'
    command = `which #{command}`.chomp

    if command.size == 0
      STDERR.puts "#{given_command}: command not found"
      next
    end
  end

  command_pid = fork do
    File.open(history_file_path, "a") { |f| f.puts(line) }

    if given_command == "eval"
      p eval(line.sub(/^eval\s+/, ''))
    elsif `file #{command}` =~ /: a .*ruby.* script text executable/

      # reload classes
      if defined?(ActionDispatch::Reloader)
        # Rails 3.1
        ActionDispatch::Reloader.cleanup!
        ActionDispatch::Reloader.prepare!
      else
        # Rails 3.0
        # pulled from Railties source, this triggers something
        ActionDispatch::Callbacks.new(Proc.new {}, false).call({})
        # ActiveSupport::DescendantsTracker.clear
        # ActiveSupport::Dependencies.clear

        # fix problem with ::Something::OtherThing resolving to ::OtherThing
        Rails.application.config.eager_load_paths.map { |p| Dir[p + '/**/*.rb'] }.flatten.each { |rb| require_dependency rb }
      end

      silence_warnings { ARGV = arguments }
      load(command)
    else
      exec line
    end
  end

  # send cntl-c to the child
  trap("INT") { Process.kill("INT", command_pid) }

  command_time = Benchmark.realtime { Process.wait(command_pid) }
  puts "#{line.size < 15 ? line : given_command} took %.2f seconds." % command_time if command_time > 0.4

  trap("INT", "DEFAULT")
end

puts