ruby: make the built-in ruby mode the default and...

... rename layer variable `ruby-use-built-in-ruby-mode` to
`ruby-enable-enh-ruby-mode`

layers/+lang/ruby/README.org

@@ -25,13 +25,12 @@ To use this contribution add it to your =~/.spacemacs=
 #+END_SRC
 
 This layer supports two different Ruby modes: Emacs' built-in Ruby Mode and
-[[https://github.com/zenspider/enhanced-ruby-mode][enh-ruby-mode]].  By default this layer enables the latter.  To switch to the
-built-in Ruby Mode set =ruby-use-built-in-ruby-mode=:
+[[https://github.com/zenspider/enhanced-ruby-mode][enh-ruby-mode]].  By default the built-in Ruby mode is enabled.  To switch to the
+=enh-ruby-mode= set =ruby-enable-enh-ruby-mode= to t:
 
 #+BEGIN_SRC emacs-lisp
-  (defun dotspacemacs/user-init ()
-    (setq-default ruby-use-built-in-ruby-mode t)
-  )
+  (defun dotspacemacs-configuration-layers ()
+     '((ruby :variables ruby-enable-enh-ruby-mode t)))
 #+END_SRC
 
 ** Prerequisites

layers/+lang/ruby/config.el

@@ -15,8 +15,8 @@
 (spacemacs|defvar-company-backends enh-ruby-mode)
 (spacemacs|defvar-company-backends ruby-mode)
 
-(defvar ruby-use-built-in-ruby-mode nil
-  "If non-nil, use built-in Ruby Mode.
+(defvar ruby-enable-enh-ruby-mode nil
+  "If non-nil, use `enh-ruby-mode' package insted of the built-in Ruby Mode.
 
 Otherwise use Enh Ruby Mode, which is the default.")
 

layers/+lang/ruby/packages.el

@@ -20,13 +20,13 @@
         ruby-test-mode
         ruby-tools))
 
+(if ruby-enable-enh-ruby-mode
+    (add-to-list 'ruby-packages 'enh-ruby-mode)
+  (add-to-list 'ruby-packages 'ruby-mode))
+
 (when ruby-version-manager
   (add-to-list 'ruby-packages ruby-version-manager))
 
-(if ruby-use-built-in-ruby-mode
-    (add-to-list 'ruby-packages 'ruby-mode)
-  (add-to-list 'ruby-packages 'enh-ruby-mode))
-
 (defun ruby/init-rbenv ()
   "Initialize RBENV mode"
   (use-package rbenv