replace an issue number with a markdown link to github issue

create-github-issue.el

(setq github-project-prefix "https://github.com/scylladb/scylla/issues/")

(defun create-github-issue (string  &optional from to)
  "replace a #xxx with [#xxx](https://github.com/scylladb/scylla/issues/xxx)"
  (interactive
   (if (use-region-p)
       (list nil (region-beginning) (region-end))
     (let ((bds (bounds-of-thing-at-point 'paragraph)) )
       (list nil (car bds) (cdr bds)) ) ) )
  (let (workOnStringP inputStr outputStr)
    (setq workOnStringP (if string t nil))
    (setq inputStr (if workOnStringP string (buffer-substring-no-properties from to)))
    (setq outputStr
          (let ((case-fold-search t))
            (replace-regexp-in-string "#\\([0-9]+\\)" (concat "[#\\1](" github-project-prefix "\\1)") inputStr)))
            (if workOnStringP
        outputStr
      (save-excursion
        (delete-region from to)
        (goto-char from)
        (insert outputStr)))))