Shell-escape a string in Elisp

shell-escaper.el

(defun ph/shell-escaper (matched-text)
    "Return replacement text for MATCHED-TEXT when shell-escaping.

See `ph/shell-escape'."
    (cond
        ;; Already escaped?
        ((string= matched-text "\\'")
            "’")
        ;; Leading?
        ((string= matched-text "'")
            "’")
        ((string-match "\\(.\\)'" matched-text)
            (concat
                (match-string 1 matched-text)
                "’"))
        ;; TODO whitespace, *, ?, {, }, (, ), [, ]
        (t
            matched-text)))

(defun ph/shell-escape (string)
    "Make STRING safe to pass to a shell command."
    (replace-regexp-in-string
        ".?'"
        #'ph/shell-escaper
        (replace-regexp-in-string "\n" " " string)))