These should allow external code to run blocks of user code to do
"work", at a similar unit size to a web request, without needing to get
intimate with ActionDipatch.
This can be turned off by setting `config.reload_classes_only_on_change` to false.
Extensions like Active Record should add their respective files like db/schema.rb and db/structure.sql to `config.watchable_files` if they want their changes to affect classes reloading.
Thanks to https://github.com/paneq/active_reload and Pastorino for the inspiration. <3
Based on the implementation on the 2-3-stable branch, patches by Hongli
Lai <hongli@phusion.nl>, and helpful suggestions from José Valim.
Hongli Lai's patches included locking around the request cycle; this is
now handled by Rack::Lock (https://github.com/rack/rack/issues/issue/87/).
[#2873]
Signed-off-by: José Valim <jose.valim@gmail.com>
