Fix ruby-mode auto-mode-alist entry

* lisp/progmodes/ruby-mode.el (auto-mode-alist): Add grouping
around the extensions (bug#21257).

1 files changed, 2 insertions, 1 deletions

diff --git a/lisp/progmodes/ruby-mode.el b/lisp/progmodes/ruby-mode.el
index 754785168f2..ab83b977320 100644
--- a/lisp/progmodes/ruby-mode.el
+++ b/lisp/progmodes/ruby-mode.el
@@ -2258,9 +2258,10 @@ See `font-lock-syntax-table'.")
 
 ;;;###autoload
 (add-to-list 'auto-mode-alist
-             (cons (purecopy (concat "\\(?:\\."
+             (cons (purecopy (concat "\\(?:\\.\\(?:"
                                      "rb\\|ru\\|rake\\|thor"
                                      "\\|jbuilder\\|rabl\\|gemspec\\|podspec"
+                                     "\\)"
                                      "\\|/"
                                      "\\(?:Gem\\|Rake\\|Cap\\|Thor"
                                      "\\|Puppet\\|Berks"