config: '%state-directory' always honors $NIX_STATE_DIR.

* guix/config.scm.in (%state-directory): Honor $NIX_STATE_DIR.
* guix/scripts/package.scm (%profile-directory): Use %state-directory
  directly.
* guix/store.scm (%default-socket-path, log-file): Likewise.

guix/config.scm.in

@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2012, 2013 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2012, 2013, 2014 Ludovic Courtès <ludo@gnu.org>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -55,7 +55,7 @@
 
 (define %state-directory
   ;; This must match `NIX_STATE_DIR' as defined in `daemon.am'.
-  "@guix_localstatedir@/nix")
+  (or (getenv "NIX_STATE_DIR") "@guix_localstatedir@/nix"))
 
 (define %config-directory
   ;; This must match `NIX_CONF_DIR' as defined in `daemon.am'.

guix/scripts/package.scm

@@ -57,7 +57,7 @@
          (cut string-append <> "/.guix-profile")))
 
 (define %profile-directory
-  (string-append (or (getenv "NIX_STATE_DIR") %state-directory) "/profiles/"
+  (string-append %state-directory "/profiles/"
                  (or (and=> (getenv "USER")
                             (cut string-append "per-user/" <>))
                      "default")))

guix/store.scm

@@ -158,8 +158,7 @@
   (delete-specific 3))
 
 (define %default-socket-path
-  (string-append (or (getenv "NIX_STATE_DIR") %state-directory)
-                 "/daemon-socket/socket"))
+  (string-append %state-directory "/daemon-socket/socket"))
 
 (define %daemon-socket-file
   ;; File name of the socket the daemon listens too.
@@ -749,12 +748,9 @@ syntactically valid store path."
 (define (log-file store file)
   "Return the build log file for FILE, or #f if none could be found.  FILE
 must be an absolute store file name, or a derivation file name."
-  (define state-dir                               ; XXX: factorize
-    (or (getenv "NIX_STATE_DIR") %state-directory))
-
   (cond ((derivation-path? file)
          (let* ((base    (basename file))
-                (log     (string-append (dirname state-dir) ; XXX: ditto
+                (log     (string-append (dirname %state-directory) ; XXX
                                         "/log/nix/drvs/"
                                         (string-take base 2) "/"
                                         (string-drop base 2)))