build a rails generator to encapsulate setup logic

* currently only appends to gitignore

README.md

@@ -23,10 +23,10 @@ Add the gem to your gemfile
 gem 'spritely'
 ```
 
-Add the following to your gitignore
+Run the generator to update your gitignore
 
-```
-app/assets/images/sprites
+```bash
+bundle exec rails generate spritely:install
 ```
 
 This directory will be created in your deployed environments when precompiling assets.

lib/generators/spritely/install_generator.rb

@@ -0,0 +1,12 @@
+require 'rails/generators/base'
+
+module Spritely
+  module Generators
+    class InstallGenerator < ::Rails::Generators::Base
+      def add_sprites_folder_to_gitignore
+        create_file '.gitignore', skip: true
+        inject_into_file '.gitignore', "\n#{Spritely.relative_folder_path}\n", after: /\z/
+      end
+    end
+  end
+end

lib/spritely.rb

@@ -8,6 +8,10 @@ def self.environment
   end
 
   def self.directory
-    ::Rails.root.join('app', 'assets', 'images', 'sprites')
+    ::Rails.root.join(relative_folder_path)
+  end
+
+  def self.relative_folder_path
+    Pathname.new(File.join('app', 'assets', 'images', 'sprites'))
   end
 end

spec/generators/spritely/install_generator_spec.rb

@@ -0,0 +1,19 @@
+require 'spec_helper'
+require 'generators/spritely/install_generator'
+
+describe Spritely::Generators::InstallGenerator, :generator do
+  destination File.expand_path("../../../../tmp", __FILE__)
+
+  before do
+    prepare_destination
+    run_generator
+  end
+
+  subject { destination_root }
+
+  it { is_expected.to have_structure {
+    file '.gitignore' do
+      contains 'app/assets/images/sprites'
+    end
+  } }
+end

spec/spec_helper.rb

@@ -1,5 +1,6 @@
 require 'rspec'
 require 'rspec/its'
+require 'generator_spec/generator_example_group'
 require 'spritely'
 
 require 'pry-byebug'
@@ -12,5 +13,6 @@
   end
 
   config.include RailsAppHelpers, :integration
+  config.include GeneratorSpec::GeneratorExampleGroup, :generator
   config.around(:each, :integration) { |example| within_rails_app(&example) }
 end

spec/spritely_spec.rb

@@ -8,8 +8,12 @@
   end
 
   describe '.directory' do
-    before { stub_const('::Rails', double(root: File)) }
+    before { stub_const('::Rails', double(root: Pathname.new('foo/bar'))) }
 
-    its(:directory) { should eq('app/assets/images/sprites') }
+    its(:directory) { should eq(Pathname.new('foo/bar/app/assets/images/sprites')) }
+  end
+
+  describe '.relative_folder_path' do
+    its(:relative_folder_path) { should eq(Pathname.new('app/assets/images/sprites')) }
   end
 end

spec/support/rails_app_helpers.rb

@@ -3,8 +3,7 @@ module RailsAppHelpers
     '--skip-active-record',
     '--skip-test-unit',
     '--skip-javascript',
-    '--skip-spring',
-    '--skip-git'
+    '--skip-spring'
   ]
 
   def within_rails_app(&block)
@@ -19,6 +18,7 @@ def within_rails_app(&block)
               f.write("gem 'spritely', path: '#{__dir__}/../../'\n")
             end
             %x(bundle install)
+            %x(rails generate spritely:install)
             FileUtils.cp_r "#{__dir__}/../fixtures/rails-app/.", "."
             yield
           end

spritely.gemspec

@@ -26,4 +26,5 @@ Gem::Specification.new do |s|
   s.add_development_dependency 'rspec', '>= 3.0'
   s.add_development_dependency 'rspec-its'
   s.add_development_dependency 'appraisal'
+  s.add_development_dependency 'generator_spec'
 end