Merge pull request #49338 from jean-francois-labbe/document-rails-new…

…-with-specific-version

[ci skip] Document how to rails new with a specific version

railties/lib/rails/generators/rails/app/USAGE

@@ -9,11 +9,18 @@ Description:
     Note that the arguments specified in the .railsrc file don't affect the
     default values shown above in this help message.
 
+    You can specify which version to use when creating a new rails application 
+    using `rails _<version>_ new`.
+
 Examples:
     `rails new ~/Code/Ruby/weblog`
 
     This generates a new Rails app in ~/Code/Ruby/weblog.
 
+    `rails _<version>_ new weblog`
+
+    This generates a new Rails app with the provided version in ./weblog.
+
     `rails new weblog --api`
 
     This generates a new Rails app in API mode in ./weblog.