Generate a new app.json file for the current project

generate_app_json.rb

#!/usr/bin/env ruby
require 'json'

# Grab info from the heroku cli
info = JSON.load(`heroku info --json`)
env_variables = JSON.load(`heroku config --json`)
buildpacks = `heroku buildpacks`.lines[1..].map{ |l| { 'url' => l[3..].chop }}
addons = JSON.load(`heroku addons --json`).inject(Hash.new{ |h, k| h[k] = [] }) { |h, e|
  name = e['addon_service']['name']
  plan = e['plan']['name']
  as = e['attachments'][0]['name']
  h[name] << { 'plan' => plan, 'as' => as }
  h
}
formation = info['dynos'].inject({}) { |h, ps|  
  type = ps['type']
  quantity = h[type] ? h[type]['quantity'] + 1 : 1
  size = ps['size'] 
  h[type] = { 'quantity' => quantity, 'size' => size }
  h
}
name = info['app']['name']
website = info['app']['web_url']
repository = info['app']['git_url']
keywords = []

scripts = {}
if File.file?('config/application.rb')
  # Rails app detected
  scripts['postdeploy'] = 'bundle exec rake db:migrate'
  keywords << 'Rails'
end

app_json = {
  'name' => name,
  'description' => '',
  'keywords' => keywords,
  'website' => website,
  'repository' => repository,
  'buildpacks' => buildpacks,
  'formation' => formation,
  'addons' => addons,
  'env' => env_variables,
  'scripts' => scripts
} 
print JSON.pretty_generate(app_json)