Add $(user -g) and whitespace

rails/README.md

@@ -55,6 +55,15 @@ run` will help you generate one. Run it in the root of your app, next to the
 
     docker run --rm -v "$(pwd)":/usr/src/app -w /usr/src/app ruby:2.1 bundle install
 
+## Bootstrap a new Rails application
+
+If you want to generate the scaffolding for a new Rails project, you can do the
+following:
+
+    docker run -it --rm --user "$(id -u):$(id -g)" -v "$(pwd)":/usr/src/app -w /usr/src/app rails rails new webapp
+
+This will create a sub-directory named `webapp` inside your current directory.
+
 # License
 
 View [license information](https://github.com/rails/rails#license)

rails/content.md

@@ -43,3 +43,12 @@ run` will help you generate one. Run it in the root of your app, next to the
 `Gemfile`:
 
     docker run --rm -v "$(pwd)":/usr/src/app -w /usr/src/app ruby:2.1 bundle install
+
+## Bootstrap a new Rails application
+
+If you want to generate the scaffolding for a new Rails project, you can do the
+following:
+
+    docker run -it --rm --user "$(id -u):$(id -g)" -v "$(pwd)":/usr/src/app -w /usr/src/app rails rails new webapp
+
+This will create a sub-directory named `webapp` inside your current directory.