There is no default setting for this, it must be set per file.
If you set it to a symbol in the file Local Variables section,
you need to add a `bug-reference-url-format' property to it:
-\(put 'my-bug-reference-url-format 'bug-reference-url-format t)
+\(put \\='my-bug-reference-url-format \\='bug-reference-url-format t)
so that it is considered safe, see `enable-local-variables'.")
;;;###autoload