README.md in rubocop-changes-0.7.0 vs README.md in rubocop-changes-0.8.0

@@ -30,10 +30,12 @@
 
     $ gem install rubocop-changes
 
 ## Usage
 
-    $ bundle exec rubocop-changes
+    $ bundle exec rubocop-changes -b master
+    
+When you run `rubocop-changes`, you have to specify which is your base branch with `-b` argument. By default is `main`. If you want to avoid to pass this argument everytime you execute this command, you can also set the `RUBOCOP_CHANGES_BASE_BRANCH` environment variable.
 
 ## Other gems
 
 There are similar projects out there, like
 [rubocop-git](https://github.com/m4i/rubocop-git),