Allow oxford commas and spaces before commas in MR issue closing pattern.

config/initializers/1_settings.rb

@@ -262,7 +262,7 @@ Settings.gitlab['signup_enabled'] ||= true if Settings.gitlab['signup_enabled'].
 Settings.gitlab['signin_enabled'] ||= true if Settings.gitlab['signin_enabled'].nil?
 Settings.gitlab['restricted_visibility_levels'] = Settings.__send__(:verify_constant_array, Gitlab::VisibilityLevel, Settings.gitlab['restricted_visibility_levels'], [])
 Settings.gitlab['username_changing_enabled'] = true if Settings.gitlab['username_changing_enabled'].nil?
-Settings.gitlab['issue_closing_pattern'] = '((?:[Cc]los(?:e[sd]?|ing)|[Ff]ix(?:e[sd]|ing)?|[Rr]esolv(?:e[sd]?|ing)|[Ii]mplement(?:s|ed|ing)?)(:?) +(?:(?:issues? +)?%{issue_ref}(?:(?:, *| +and +)?)|([A-Z][A-Z0-9_]+-\d+))+)' if Settings.gitlab['issue_closing_pattern'].nil?
+Settings.gitlab['issue_closing_pattern'] = '((?:[Cc]los(?:e[sd]?|ing)|[Ff]ix(?:e[sd]|ing)?|[Rr]esolv(?:e[sd]?|ing)|[Ii]mplement(?:s|ed|ing)?)(:?) +(?:(?:issues? +)?%{issue_ref}(?:(?: *,? +and +| *, *)?)|([A-Z][A-Z0-9_]+-\d+))+)' if Settings.gitlab['issue_closing_pattern'].nil?
 Settings.gitlab['default_projects_features'] ||= {}
 Settings.gitlab['webhook_timeout'] ||= 10
 Settings.gitlab['max_attachment_size'] ||= 10

spec/lib/gitlab/closing_issue_extractor_spec.rb

@@ -365,6 +365,20 @@ describe Gitlab::ClosingIssueExtractor do
             .to match_array([issue, other_issue, third_issue])
       end
 
+      it 'allows oxford commas (comma before and) when referencing multiple issues' do
+        message = "Closes #{reference}, #{reference2}, and #{reference3}"
+
+        expect(subject.closed_by_message(message))
+            .to match_array([issue, other_issue, third_issue])
+      end
+
+      it 'allows spaces before commas when referencing multiple issues' do
+        message = "Closes #{reference} , #{reference2} , and #{reference3}"
+
+        expect(subject.closed_by_message(message))
+            .to match_array([issue, other_issue, third_issue])
+      end
+
       it 'fetches issues in multi-line message' do
         message = "Awesome commit (closes #{reference})\nAlso fixes #{reference2}"