load the environment once and run tasks

taskrunner.rb

#!/usr/bin/env ruby

# Move this script to RAILS_ROOT/scripts/taskrunner, `chmod +x` it and run with ./script/taskrunner
# run one or more rake tasks `Task:> db:migrate app:do_something env_variables=like_this`

require 'readline'
require 'irb'
require './config/environment'
load './Rakefile'

while task = Readline.readline('Tasks:> ', true)
  begin
    exit if task =~ /^exit/
    puts 'Reloading...'
    version = Rails.version
    if version =~ /^2/
      ActiveSupport::Dependencies.clear
    elsif version =~ /^3/
      ActionDispatch::Callbacks.new(Proc.new {}, false).call({})
    end

    task.gsub!(/\n+$/,'')

    # set env variables
    env = task.scan(/\w+=\w+/)
    env.each do |env_var|
      varname, value = env_var.split('=')
      ENV[varname] = value
    end

    # remove env variables from task list
    tasks = task.gsub(/\w+=\w+/, '').split(/\s+/)

    begin
      tasks.each do |task|
        if raketask = Rake::Task[task]
          puts "running '#{task}'"
          raketask.invoke
          raketask.reenable
          Rake::Task.tasks.each {|t| t.reenable unless t.to_s == 'environment'}
        end
      end

      # clear env variables
      env.each do |env_var|
        varname, value = env_var.split('=')
        ENV[varname] = nil
      end

    rescue Interrupt => e
      nil
    rescue Exception => e
      puts e.message
      puts e.inspect
    end
  rescue Interrupt => e
    exit
  end
end