Do not TSort Finisher and Bootstrap initializers

[cameel]

• Use sorting in topological order (TSort) on all initializers found by Railtie but not on the ones from Rails::Application::Bootstrap and Rails::Application::Finisher. Bootstrap should always be the first and Finisher the last.
• Move Rails::Initializable::Collection to Rails::Application. Now it's only needed there.

This fixes issue 1587 reported by me yesterday.

[vijaydev]

Suggestion: It will be useful to mention the issue number itself as the link text in "This fixes <issue-num>" :-)

[cameel]

ok. link fixed.

[josevalim]

I am afraid that, after this change, people won't be able to use before/after using bootstrap and finisher as references. Also, I don't agree with the TSort responsibility moving to the application object. Maybe cells should be using the finisher hooks and/or passing both before/after instead of just one?

[cameel]

Right, it might be better for Cells to use :after_initialize hook rather than initializers. Even though it explicitly states in its Railtie that it wants to run after Finisher's :set_routes_reloader initializer, it seems to work fine with my patch that always places it before the Finisher. I'll report it in their repo.

Still, the issue with :after_initialize remains. There should be more constraints on :finisher_hook so that other initializers can't push it down.

And is :after_initialize really a good name for this hook? It's misleading since it's not guaranteed to run after all initializers. At very least :set_routes_reloader and :disable_dependency_loading initializers from Finisher run after the hooks. Moreover, it's possible for an initializer to request to be run after :finisher_hook. This can be a source or errors (as this issue clearly shows).

Or maybe :after_initialize would better not be executed by an initializer?