Merge pull request #216983 from ncfavier/showOption-comment

  # Helper functions.

  /* Convert an option, described as a list of the option parts in to a

     safe, human readable version.

  /* Convert an option, described as a list of the option parts to a

     human-readable version.

     Example:

       (showOption ["foo" "bar" "baz"]) == "foo.bar.baz"

       (showOption ["foo" "bar.baz" "tux"]) == "foo.bar.baz.tux"

       (showOption ["foo" "bar.baz" "tux"]) == "foo.\"bar.baz\".tux"

       (showOption ["windowManager" "2bwm" "enable"]) == "windowManager.\"2bwm\".enable"

     Placeholders will not be quoted as they are not actual values:

       (showOption ["foo" "*" "bar"]) == "foo.*.bar"

       (showOption ["foo" "<name>" "bar"]) == "foo.<name>.bar"

     Unlike attributes, options can also start with numbers:

       (showOption ["windowManager" "2bwm" "enable"]) == "windowManager.2bwm.enable"

  */

  showOption = parts: let

    escapeOptionPart = part: