JIRA project identifiers may also contain dashes '-'

lib/gitlab/markdown.rb

@@ -98,7 +98,7 @@ module Gitlab
       (?<prefix>\W)?                         # Prefix
       (                                      # Reference
          @(?<user>[a-zA-Z][a-zA-Z0-9_\-\.]*) # User name
-        |\#(?<issue>([a-zA-Z]+-)?\d+)        # Issue ID
+        |\#(?<issue>([a-zA-Z\-]+-)?\d+)      # Issue ID
         |!(?<merge_request>\d+)              # MR ID
         |\$(?<snippet>\d+)                   # Snippet ID
         |(?<commit>[\h]{6,40})               # Commit ID