Make the dummy app available to bin/console

Usage example:

$ bin/console
USAGE:
  dummy_app             # Load the dummy app and return the Rails.application instance
  dummy_app.initialize! # Initialize the dummy app
  dummy_app.migrate!    # Run all the dummy app migrations
>> dummy_app
Loading the dummy app...done.
=> #<DummyApp::Application root=/Users/elia/Code/Nebulab/solidus>
>> dummy_app.initialize!
=> #<DummyApp::Application root=/Users/elia/Code/Nebulab/solidus>
>> dummy_app.migrate!
== 20100107141738 AddApiKeyToSpreeUsers: migrating ============================
-- add_column(:spree_users, :api_key, :string, {:limit=>40})
   -> 0.0019s
== 20100107141738 AddApiKeyToSpreeUsers: migrated (0.0020s) ===================

...

== 20190220093635 DropSpreeStoreCreditUpdateReasons: migrating ================
-- table_exists?(:spree_store_credit_update_reasons)
   -> 0.0003s
-- drop_table(:spree_store_credit_update_reasons)
   -> 0.0002s
-- column_exists?(:spree_store_credit_events, :update_reason_id)
   -> 0.0004s
-- remove_column(:spree_store_credit_events, :update_reason_id)
   -> 0.0075s
== 20190220093635 DropSpreeStoreCreditUpdateReasons: migrated (0.0084s) =======

=> #<DummyApp::Application root=/Users/elia/Code/Nebulab/solidus>
>>

bin/console

@@ -4,12 +4,48 @@
 require "bundler/setup"
 require "solidus"
 
-# You can add fixtures and/or initialization code here to make experimenting
-# with your gem easier. You can also use a different console, if you like.
+module IRBSolidusHelpers
+  def dummy_app
+    @dummy_app ||= begin
+      print "Loading the dummy app..."
+      ENV['DATABASE_URL'] ||= 'sqlite3::memory:?pool=1'
 
-# (If you use this, don't forget to add pry to your Gemfile!)
-# require "pry"
-# Pry.start
+      require "spree/testing_support/dummy_app"
+
+      class << (Rails.application)
+        # Allow to run migrations from the console
+        def migrate!
+          ActiveRecord::Migrator.migrations_paths =
+            Rails.application.migration_railties.flat_map do |engine|
+              (engine.paths['db/migrate'] if engine.respond_to?(:paths)).to_a
+            end
+          ActiveRecord::Migration.verbose = false
+          ActiveRecord::Base.connection.migration_context.run(:up, '20160101010000_solidus_one_four'.to_i)
+          ActiveRecord::Tasks::DatabaseTasks.migrate
+          self
+        end
+
+        # Avoid flooding the console with the original #inspect
+        def inspect
+          "#<#{self.class.name} root=#{root}>"
+        end
+      end
+
+      puts "done."
+      Rails.application
+    end
+  end
+
+  USAGE = <<~TXT
+    USAGE:
+      dummy_app             # Load the dummy app and return the Rails.application instance
+      dummy_app.initialize! # Initialize the dummy app
+      dummy_app.migrate!    # Run all the dummy app migrations
+  TXT
+end
+
+puts IRBSolidusHelpers::USAGE
 
 require "irb"
+IRB::ExtendCommandBundle.prepend IRBSolidusHelpers
 IRB.start(__FILE__)