Update app to use environment variable RAILS_DATAROOT

Theses are directions for updating an app that was built prior to the introduction of the awesim_rails gem.

While developing apps, we previously used the default db location $RAILS_APP_ROOT/db/development.sqlite3 and used OSC::Machete::Crimson object to give the crimson files path where we stored user files, which was $HOME/crimson_files/APP_NAME/. This will no longer work.

See Rationale for RAILS_DATAROOT for an explanation.

1. Add these gems to your Gemfile and use the latest osc-machete gem:

gem 'dotenv-rails', '~> 2.0.0'
gem 'awesim_rails', '~> 0.6.0'
gem 'osc-machete', '~> 0.6.2'

gem 'rails_12factor', group: :production

2. Update code to use AwesimRails.dataroot

awesim_rails introduces AwesimRails.dataroot which replaces OSC::Machete::Crimson#files_path. osc-machete v0.5.0 removes OSC::Machete::Crimson.

1. Update paperclip initializer config/initializers/paperclip.rb

+++ b/config/initializers/paperclip.rb
@@ -5,7 +5,7 @@ Paperclip.options[:content_type_mappings] = {
 }
 
 # We use ":class/:id/:created_at/" to specify path uniqueness
-Paperclip::Attachment.default_options[:path] = "#{ENV['HOME']}/crimson_files/ContainerFillSim/uploads/:class/:id/:created_at/:attachment/:filename"
+Paperclip::Attachment.default_options[:path] = "#{AwesimRails.dataroot}/uploads/:class/:id/:created_at/:attachment/:filename"
 
 # URL location points to file mount in routes called "/files"
 # therefore this mirrors ':path' to some extent

2. Update config/routes.rb - awesim_rails automatically mounts this at '/files':

diff --git a/config/routes.rb b/config/routes.rb
index ad63f0b..0794d6d 100644
--- a/config/routes.rb
+++ b/config/routes.rb
@@ -13,9 +13,6 @@ ContainerFillSim::Application.routes.draw do
 
   root 'containers#index'
 
-  #FIXME: add as a separate object that we can mount in osc-machete-rails
-  mount proc { |env| Rack::Directory.new(OSC::Machete::Crimson.new(Rails.application.class.parent_name).files_path).call(env) } => "/files"
-
   # The priority is based upon order of creation: first created -> highest priority.
   # See how all your routes lay out with "rake routes".

3. Replace in your code wherever OSC::Machete::Crimson is used with AwesimRails.dataroot. AwesimRails.dataroot is a Pathname object just like Rails.root is, so you can do something like outdir = AwesimRails.dataroot.join("vnc", "paraview") which is a line from the updated version of ContainerFillSim

3. Set RAILS_DATAROOT env var in .env.development code to use AwesimRails.dataroot

AwesimRails.dataroot by default is set to the environment variable RAILS_DATAROOT. Add .env.development to the root of your project with this content:

export RAILS_DATAROOT=$HOME/crimson_files/ContainerFillSim