rails-generate: add migration (#3975)

pages/common/rails-generate.md

@@ -1,19 +1,24 @@
 # rails generate
 
 > Generate new Rails templates in an existing project.
+> More information: <https://guides.rubyonrails.org/command_line.html#rails-generate>.
 
 - List all available generators:
 
 `rails generate`
 
-- Generate a new model:
+- Generate a new model named Post with attributes title and body:
 
-`rails generate model {{model_name}}`
+`rails generate model {{Post}} {{title:string}} {{body:text}}`
 
-- Generate a new controller:
+- Generate a new controller named Posts with actions index, show, new and create:
 
-`rails generate controller {{controller_name}}`
+`rails generate controller {{Posts}} {{index}} {{show}} {{new}} {{create}}`
 
-- Generate a scaffold for a new model:
+- Generate a new migration that adds a category attribute to an existing model called Post:
 
-`rails generate scaffold {{model_name}}`
+`rails generate migration {{AddCategoryToPost}} {{category:string}}`
+
+- Generate a scaffold for a model named Post, predefining the attributes title and body:
+
+`rails generate scaffold {{Post}} {{title:string}} {{body:text}}`