Implement .isolator_ignore.yml configuration file support

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ## master
 
+- Add .isolator_ignore.yml configuration file for Rails application.
+
 ## 0.7.0 (2020-09-25)
 
 - Add debug mode. ([@palkan][])

README.md

@@ -161,7 +161,7 @@ You can add as many _ignores_ as you want, the offense is registered iff all of
 
 ### Using with legacy Rails codebases
 
-If you already have a huge Rails project it can be tricky to turn Isolator on because you'll immediately get a lot of failed specs. If you want to fix detected issues one by one, you can list all of them in the special file `.isolator_todo.yml` in the following way:
+If you already have a huge Rails project it can be tricky to turn Isolator on because you'll immediately get a lot of failed specs. If you want to fix detected issues one by one, you can list all of them in the special files `.isolator_todo.yml` and `.isolator_ignore.yml` in the following way:
 
 ```
 sidekiq:
@@ -171,6 +171,8 @@ sidekiq:
 
 All the exceptions raised in the listed lines will be ignored.
 
+The `.isolator_todo.yml` file is intended to point to the code that should be fixed later, and `.isolator_ignore.yml` points to the code that for some reasons is not expected to be fixed. (See https://github.com/palkan/isolator/issues/40)
+
 ### Using with legacy Ruby codebases
 
 If you are not using Rails, you'll have to load ignores from file manually, using `Isolator::Ignorer.prepare(path:)`, for instance `Isolator::Ignorer.prepare(path: "./config/.isolator_todo.yml")`

lib/isolator/railtie.rb

@@ -16,6 +16,7 @@ class Railtie < ::Rails::Railtie # :nodoc:
       load File.join(__dir__, "adapters.rb")
 
       Isolator.config.ignorer&.prepare
+      Isolator.config.ignorer&.prepare(path: ".isolator_ignore.yml")
 
       next unless Rails.env.test?