gnu: shadow: Take the source from Git.

* gnu/packages/admin.scm (shadow)[source]: Use the git repo.

gnu/packages/admin.scm

@@ -22,6 +22,7 @@ (define-module (gnu packages admin)
   #:use-module (guix licenses)
   #:use-module (guix packages)
   #:use-module (guix download)
+  #:use-module (guix git-download)
   #:use-module (guix build-system cmake)
   #:use-module (guix build-system gnu)
   #:use-module (guix build-system trivial)
@@ -164,13 +165,15 @@ (define-public shadow
     (name "shadow")
     (version "4.1.5.1")
     (source (origin
-             (method url-fetch)
-             (uri (string-append
-                   "http://pkg-shadow.alioth.debian.org/releases/shadow-"
-                   version ".tar.bz2"))
+             ;; Shadow has no real upstream, and not even tarballs.
+             ;; See <https://lists.gnu.org/archive/html/guix-devel/2014-03/msg00233.html>.
+             (method git-fetch)
+             (uri (git-reference
+                   (url "git://git.debian.org/git/pkg-shadow/shadow")
+                   (commit (string-append "upstream/" version))))
              (sha256
               (base32
-               "1yvqx57vzih0jdy3grir8vfbkxp0cl0myql37bnmi2yn90vk6cma"))))
+               "1xx85d83kmacmjzqbamgydcjkwsqd5fi1s2wgwx6myq5wa39qx0n"))))
     (build-system gnu-build-system)
     (arguments
      '(;; Assume System V `setpgrp (void)', which is the default on GNU