Address Yorick's feedback

Signed-off-by: Rémy Coutable <remy@rymai.me>

CHANGELOG

@@ -2,8 +2,6 @@ Please view this file on the master branch, on stable branches it's out of date.
 
 v 8.8.0 (unreleased)
   - Implement GFM references for milestones (Alejandro Rodríguez)
-
-v 8.7.1 (unreleased)
   - Snippets tab under user profile. !4001 (Long Nguyen)
   - Fix error when using link to uploads in global snippets
   - Assign labels and milestone to target project when moving issue. !3934 (Long Nguyen)

app/models/milestone.rb

@@ -67,7 +67,7 @@ class Milestone < ActiveRecord::Base
     # NOTE: The iid pattern only matches when all characters on the expression
     # are digits, so it will match %2 but not %2.1 because that's probably a
     # milestone name and we want it to be matched as such.
-    %r{
+    @reference_pattern ||= %r{
       (#{Project.reference_pattern})?
       #{Regexp.escape(reference_prefix)}
       (?:
@@ -195,7 +195,7 @@ class Milestone < ActiveRecord::Base
   private
 
   def milestone_format_reference(format = :iid)
-    raise StandardError, 'Unknown format' unless [:iid, :name].include?(format)
+    raise ArgumentError, 'Unknown format' unless [:iid, :name].include?(format)
 
     if format == :name && !name.include?('"')
       %("#{name}")