Define most options in external config file, with ability to override

.gitignore

@@ -79,3 +79,4 @@ tmtags
 ### Other Files ###
 *.log
 /roles/*
+/config.yml

Gemfile

@@ -6,3 +6,4 @@ gem 'rspec',      '~> 3.3'
 gem 'serverspec', '~> 2.24'
 gem 'net-ssh',    '~> 4.0'
 gem 'docker-api', '~> 1.33'
+gem 'deep_merge', '~> 1.2'

Gemfile.lock

@@ -1,6 +1,7 @@
 GEM
   remote: https://rubygems.org/
   specs:
+    deep_merge (1.2.1)
     diff-lcs (1.3)
     docker-api (1.34.2)
       excon (>= 0.47.0)
@@ -45,6 +46,7 @@ PLATFORMS
 
 DEPENDENCIES
   bundler (~> 1.15)
+  deep_merge (~> 1.2)
   docker-api (~> 1.33)
   net-ssh (~> 4.0)
   rake (~> 12.0)

Vagrantfile

@@ -1,23 +1,49 @@
 # -*- mode: ruby -*-
 # vi: set ft=ruby :
 
-Vagrant.configure('2') do |config|
-  config.vm.define 'trusty' do |trusty|
-    trusty.vm.box = 'ubuntu/trusty64'
-  end
+require "yaml"
 
-  config.vm.define 'xenial' do |xenial|
-    xenial.vm.box = 'ubuntu/xenial64'
-  end
+default_config_file = File.join(File.dirname(__FILE__), "config.yml.dist")
+local_config_file   = File.join(File.dirname(__FILE__), "config.yml")
+
+config_data = YAML.load_file default_config_file
+config_data = Vagrant::Util::DeepMerge.deep_merge(config_data, YAML.load_file(local_config_file)) if File.exists? local_config_file
+
+Vagrant.configure("2") do |config|
+  ["trusty", "xenial", "bionic"].each do |distro|
+    config.vm.define distro do |target_env|
+      vm_config = Vagrant::Util::DeepMerge.deep_merge config_data["vm"]["global"], config_data["vm"][distro]
+
+      target_env.vm.box = vm_config["box"]
 
-  config.vm.define 'bionic' do |xenial|
-    xenial.vm.box = 'ubuntu/bionic64'
+      target_env.vm.provider :virtualbox do |vb, override|
+        vb.memory = vm_config["ram"]
+        vb.cpus   = vm_config["num_cpus"]
+
+        vb.linked_clone = true
+      end
+
+      target_env.vm.provider :vmware_fusion do |vmw, override|
+        vmw.vmx["memsize"]  = vm_config["ram"]
+        vmw.vmx["numvcpus"] = vm_config["num_cpus"]
+      end
+
+      target_env.vm.provider :parallels do |p, override|
+        p.memory = vm_config["ram"]
+        p.cpus   = vm_config["num_cpus"]
+
+        p.check_guest_tools  = false
+        p.update_guest_tools = false
+      end
+    end
   end
 
   config.vm.provision :ansible do |ansible|
     ansible.playbook = "provision-playbook.yml"
 
     ansible.compatibility_mode = "2.0"
+
+    ansible.extra_vars = config_data["ansible"]["vars"]
   end
 
   if Vagrant.has_plugin? 'vagrant-vbguest'

config.yml.dist

@@ -0,0 +1,14 @@
+---
+vm:
+  global:
+    ram: 1024
+    num_cpus: 2
+  trusty:
+    box: ubuntu/trusty64
+  xenial:
+    box: ubuntu/xenial64
+  bionic:
+    box: ubuntu/bionic64
+ansible:
+  vars:
+    swapfile_size: 1G

spec/lib/docker_env.rb

@@ -1,5 +1,8 @@
 require "docker"
 require "tempfile"
+require "yaml"
+require "deep_merge"
+require "json"
 
 class DockerEnv
   attr_reader :name, :image
@@ -14,13 +17,19 @@ def up
   end
 
   def provision
+    default_config_file = File.join(File.dirname(File.dirname(File.dirname(__FILE__))), "config.yml.dist")
+    local_config_file   = File.join(File.dirname(File.dirname(File.dirname(__FILE__))), "config.yml")
+
+    config_data = YAML.load_file default_config_file
+    config_data.deep_merge!(YAML.load_file local_config_file) if File.exists? local_config_file
+
     inventory = Tempfile.new("inventory")
 
     inventory << inventory_line
 
     inventory.close
 
-    command = "ansible-playbook", "-i", inventory.path, "-l", @name, "provision-playbook.yml"
+    command = "ansible-playbook", "-i", inventory.path, "-l", @name, "provision-playbook.yml", "-e", config_data["ansible"]["vars"].to_json
 
     output = []
     IO.popen(command, {:err => [:child, :out]}) do |io|