Activate RuboCop manual todos if envvar REVEAL_RUBOCOP_TODO is set

.rubocop.yml

@@ -7,8 +7,10 @@ require:
   - rubocop-rspec
 
 inherit_from:
-  - .rubocop_manual_todo.yml
-  - .rubocop_todo.yml
+  <% unless ENV['REVEAL_RUBOCOP_TODO'] == '1' %>
+  - '.rubocop_manual_todo.yml'
+  - '.rubocop_todo.yml'
+  <% end %>
   - ./rubocop/rubocop-migrations.yml
   - ./rubocop/rubocop-usage-data.yml
   - ./rubocop/rubocop-code_reuse.yml

doc/development/contributing/style_guides.md

@@ -154,6 +154,13 @@ resolved and place it in the `.rubocop_manual_todo.yml`. In this scenario, do no
 changes to the `.rubocop_todo.yml` as an `exclude limit` that is higher than 15 will make the
 `.rubocop_todo.yml` hard to parse.
 
+### Reveal existing RuboCop exceptions
+
+To reveal existing RuboCop exceptions in the code that have been excluded via `.rubocop_todo.yml` and
+`.rubocop_manual_todo.yml`, set the environment variable `REVEAL_RUBOCOP_TODO` to `1`.
+
+This allows you to reveal existing RuboCop exceptions during your daily work cycle and fix them along the way.
+
 ## Database migrations
 
 See the dedicated [Database Migrations Style Guide](../migration_style_guide.md).