Vagrant providers from YAML config

config.yml

---
vagrant:
  provider:
    digital_ocean:
      provider:
        token: 'YOUR TOKEN'
        image: 'ubuntu-14-04-x64'
        region: 'nyc3'
        size: '1gb'
      override:
        ssh:
          private_key_path: '~/.ssh/id_rsa'
        vm:
          box: 'digital_ocean'
          box_url: "https://github.com/smdahlen/vagrant-digitalocean/raw/master/box/digital_ocean.box"

Vagrantfile

VAGRANTFILE_API_VERSION = "2"
CURRENT_DIR = File.dirname(File.expand_path(__FILE__))
CONFIG_FILE = "#{CURRENT_DIR}/config.yml"
CONFIG_FILE_LOCAL = "#{CURRENT_DIR}/config_local.yml"

if File.exist?(CONFIG_FILE)
    require 'yaml'
    data = YAML.load_file(CONFIG_FILE)
    if File.exist?(CONFIG_FILE_LOCAL)
        class Hash
            def recursive_merge(h)
                self.merge!(h) {|key, _old, _new| if _old.class == Hash then _old.recursive_merge(_new) else _new end  }
            end
        end
        local_data = YAML::load_file(CONFIG_FILE_LOCAL)
        data.recursive_merge(local_data)
        puts "Using config with local file"
    else
        puts "Using default config file"
    end

    if data['vagrant']
        data = data['vagrant']
    end
end

def recursive_set(obj, value, current_key='', separator='.')
  if value.is_a?(Hash)
    value.each do |key, val|
      ckey = current_key.size > 0 ? "#{current_key}#{separator}#{key}" : "#{key}"
      recursive_set obj, val, ckey
    end
  else
    current_key = current_key ? "#{separator}#{current_key}" : ""
    if value.is_a?(String)
      eval "obj#{current_key}='#{value}'"
    else
      eval "obj#{current_key}=#{value}"
    end
  end
end

Vagrant.configure(VAGRANTFILE_API_VERSION) do |config|

  # This box was found at https://cloud-images.ubuntu.com/vagrant/
  config.vm.box_url = "http://cloud-images.ubuntu.com/vagrant/trusty/current/trusty-server-cloudimg-amd64-vagrant-disk1.box"
  config.vm.box = "ubuntu1404server"

  # Providers
  if data['provider'].is_a?(Hash)
    data['provider'].each do |provider_key, provider_args|
      config.vm.provider "#{provider_key}" do |provider, override|
        recursive_set provider, provider_args['provider']
        recursive_set override, provider_args['override']
      end
    end
  end
end