Suggestion: adding version information to Emacs packages

[Giap Tran]

Dear Guix Developers,

I would like to suggest adding version information to the Guix packages for 
Emacs. 
This would make it easier to know which version is installed,
upgrade/downgrade easily, and avoid confusion with version set to 0.0.0.

This is an example I'm using the version in Guix package to Emacs.

--8<---------------cut here---------------start------------->8---
    (arguments
     `(#:phases
       (modify-phases %standard-phases
         (add-after
             'unpack 'fix-version
           (lambda _
             (substitute*
                 (string-append (string-drop ,name (string-length "emacs-")) 
".el")
               (("^;; Version: ([^/[:blank:]\r\n]*)(.*)$")
                (string-append ";; Version: " ,version "\n"))))))))
--8<---------------cut here---------------end--------------->8---

Best regards,
-- 
Giap Tran <txgvnn@gmail.com>
GnuPG/0xE655BF766A56995D