Backport Jira issue key regex

app/models/project_services/jira_service.rb

@@ -31,7 +31,7 @@ class JiraService < IssueTrackerService
 
   # {PROJECT-KEY}-{NUMBER} Examples: JIRA-1, PROJECT-1
   def self.reference_pattern(only_long: true)
-    @reference_pattern ||= /(?<issue>\b([A-Z][A-Z0-9_]+-)\d+)/
+    @reference_pattern ||= /(?<issue>\b#{Gitlab::Regex.jira_issue_key_regex})/
   end
 
   def initialize_properties

lib/gitlab/regex.rb

@@ -94,6 +94,12 @@ module Gitlab
       }mx
     end
 
+    # Based on Jira's project key format
+    # https://confluence.atlassian.com/adminjiraserver073/changing-the-project-key-format-861253229.html
+    def jira_issue_key_regex
+      @jira_issue_key_regex ||= /[A-Z][A-Z_0-9]+-\d+/
+    end
+
     def jira_transition_id_regex
       @jira_transition_id_regex ||= /\d+/
     end