Add "guix pull".

* guix/scripts/pull.scm: New file.
* Makefile.am (MODULES): Add it.
* doc/guix.texi (Invoking guix pull): New node.
  (Invoking guix package): Add cross-ref to it.
* guix/ui.scm (config-directory): New procedure.
* scripts/guix.in: When `GUIX_UNINSTALLED' is undefined, add
  $XDG_CONFIG_HOME/guix/latest to the search path.
* po/POTFILES.in: Add guix/scripts/pull.scm.

Makefile.am

@@ -30,6 +30,7 @@ MODULES =					\
   guix/scripts/import.scm			\
   guix/scripts/package.scm			\
   guix/scripts/gc.scm				\
+  guix/scripts/pull.scm				\
   guix/base32.scm				\
   guix/utils.scm				\
   guix/derivations.scm				\

doc/guix.texi

@@ -393,6 +393,7 @@ management tools it provides.
 * Features::                    How Guix will make your life brighter.
 * Invoking guix package::       Package installation, removal, etc.
 * Invoking guix gc::            Running the garbage collector.
+* Invoking guix pull::          Fetching the latest Guix and distribution.
 @end menu
 
 @node Features
@@ -521,6 +522,11 @@ Remove @var{package}.
 @itemx -u @var{regexp}
 Upgrade all the installed packages matching @var{regexp}.
 
+Note that this upgrades package to the latest version of packages found
+in the distribution currently installed.  To update your distribution,
+you should regularly run @command{guix pull} (@pxref{Invoking guix
+pull}).
+
 @item --roll-back
 Roll back to the previous @dfn{generation} of the profile---i.e., undo
 the last transaction.
@@ -654,6 +660,33 @@ Show the list of live store files and directories.
 @end table
 
 
+@node Invoking guix pull
+@section Invoking @command{guix pull}
+
+Packages are installed or upgraded to the latest version available in
+the distribution currently available on your local machine.  To update
+that distribution, along with the Guix tools, you must run @command{guix
+pull}: the command downloads the latest Guix source code and package
+descriptions, and deploys it.
+
+On completion, @command{guix package} will use packages and package
+versions from this just-retrieved copy of Guix.  Not only that, but all
+the Guix commands and Scheme modules will also be taken from that latest
+version.  New @command{guix} sub-commands added by the update also
+become available.
+
+The @command{guix pull} command is usually invoked with no arguments,
+but it supports the following options:
+
+@table @code
+@item --verbose
+Produce verbose output, writing build logs to the standard error output.
+
+@item --bootstrap
+Use the bootstrap Guile to build the latest Guix.  This option is only
+useful to Guix developers.
+@end table
+
 @c *********************************************************************
 @node Programming Interface
 @chapter Programming Interface

guix/scripts/pull.scm

@@ -0,0 +1,222 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2013 Ludovic Courtès <ludo@gnu.org>
+;;;
+;;; This file is part of GNU Guix.
+;;;
+;;; GNU Guix is free software; you can redistribute it and/or modify it
+;;; under the terms of the GNU General Public License as published by
+;;; the Free Software Foundation; either version 3 of the License, or (at
+;;; your option) any later version.
+;;;
+;;; GNU Guix is distributed in the hope that it will be useful, but
+;;; WITHOUT ANY WARRANTY; without even the implied warranty of
+;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;;; GNU General Public License for more details.
+;;;
+;;; You should have received a copy of the GNU General Public License
+;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
+
+(define-module (guix scripts pull)
+  #:use-module (guix ui)
+  #:use-module (guix store)
+  #:use-module (guix config)
+  #:use-module (guix packages)
+  #:use-module (guix derivations)
+  #:use-module (guix build download)
+  #:use-module (gnu packages base)
+  #:use-module ((gnu packages bootstrap)
+                #:select (%bootstrap-guile))
+  #:use-module (gnu packages compression)
+  #:use-module (gnu packages gnupg)
+  #:use-module (srfi srfi-1)
+  #:use-module (srfi srfi-11)
+  #:use-module (srfi srfi-37)
+  #:export (guix-pull))
+
+(define %snapshot-url
+  "http://hydra.gnu.org/job/guix/master/tarball/latest/download"
+  ;;"http://git.savannah.gnu.org/cgit/guix.git/snapshot/guix-master.tar.gz"
+  )
+
+(define (download-and-store store)
+  "Download the latest Guix tarball, add it to STORE, and return its store
+path."
+  ;; FIXME: Authenticate the downloaded file!
+  ;; FIXME: Optimize data transfers using rsync, Git, bsdiff, or GNUnet's DHT.
+  (call-with-temporary-output-file
+   (lambda (temp port)
+     (let ((result
+            (parameterize ((current-output-port (current-error-port)))
+              (url-fetch %snapshot-url temp))))
+       (close port)
+       (and result
+            (add-to-store store "guix-latest.tar.gz" #f "sha256" temp))))))
+
+(define (unpack store tarball)
+  "Return a derivation that unpacks TARBALL into STORE and compiles Scheme
+files."
+  (define builder
+    `(begin
+       (use-modules (guix build utils)
+                    (system base compile)
+                    (ice-9 ftw)
+                    (ice-9 match))
+
+       (let ((out     (assoc-ref %outputs "out"))
+             (tar     (assoc-ref %build-inputs "tar"))
+             (gzip    (assoc-ref %build-inputs "gzip"))
+             (gcrypt  (assoc-ref %build-inputs "gcrypt"))
+             (tarball (assoc-ref %build-inputs "tarball")))
+         (setenv "PATH" (string-append tar "/bin:" gzip "/bin"))
+
+         (system* "tar" "xvf" tarball)
+         (match (scandir "." (lambda (name)
+                               (and (not (member name '("." "..")))
+                                    (file-is-directory? name))))
+           ((dir)
+            (chdir dir))
+           (x
+            (error "tarball did not produce a single source directory" x)))
+
+         (format #t "copying and compiling Guix to `~a'...~%" out)
+
+         ;; Copy everything under guix/ and gnu/ plus guix.scm.
+         (file-system-fold (lambda (dir stat result) ; enter?
+                             (or (string-prefix? "./guix" dir)
+                                 (string-prefix? "./gnu" dir)
+                                 (string=? "." dir)))
+                           (lambda (file stat result) ; leaf
+                             (when (or (not (string=? (dirname file) "."))
+                                       (string=? (basename file) "guix.scm"))
+                               (let ((target (string-drop file 1)))
+                                 (copy-file file
+                                            (string-append out target)))))
+                           (lambda (dir stat result) ; down
+                             (mkdir (string-append out
+                                                   (string-drop dir 1))))
+                           (const #t)             ; up
+                           (const #t)             ; skip
+                           (lambda (file stat errno result)
+                             (error "cannot access file"
+                                    file (strerror errno)))
+                           #f
+                           "."
+                           lstat)
+
+         ;; Add a fake (guix config) module to allow the other modules to be
+         ;; compiled.  The user's (guix config) is the one that will be used.
+         (copy-file "guix/config.scm.in"
+                    (string-append out "/guix/config.scm"))
+         (substitute* (string-append out "/guix/config.scm")
+           (("@LIBGCRYPT@")
+            (string-append gcrypt "/lib/libgcrypt")))
+
+         ;; Augment the search path so Scheme code can be compiled.
+         (set! %load-path (cons out %load-path))
+         (set! %load-compiled-path (cons out %load-compiled-path))
+
+         ;; Compile the .scm files.
+         (for-each (lambda (file)
+                     (when (string-suffix? ".scm" file)
+                       (let ((go (string-append (string-drop-right file 4)
+                                                ".go")))
+                         (compile-file file
+                                       #:output-file go
+                                       #:opts %auto-compilation-options))))
+                   (find-files out "\\.scm"))
+
+         ;; Remove the "fake" (guix config).
+         (delete-file (string-append out "/guix/config.scm"))
+         (delete-file (string-append out "/guix/config.go")))))
+
+  (build-expression->derivation store "guix-latest" (%current-system)
+                                builder
+                                `(("tar" ,(package-derivation store tar))
+                                  ("gzip" ,(package-derivation store gzip))
+                                  ("gcrypt" ,(package-derivation store
+                                                                 libgcrypt))
+                                  ("tarball" ,tarball))
+                                #:modules '((guix build utils))))
+
+
+;;;
+;;; Command-line options.
+;;;
+
+(define %default-options
+  ;; Alist of default option values.
+  '())
+
+(define (show-help)
+  (display (_ "Usage: guix pull [OPTION]...
+Download and deploy the latest version of Guix.\n"))
+  (display (_ "
+      --verbose          produce verbose output"))
+  (display (_ "
+      --bootstrap        use the bootstrap Guile to build the new Guix"))
+  (newline)
+  (display (_ "
+  -h, --help             display this help and exit"))
+  (display (_ "
+  -V, --version          display version information and exit"))
+  (newline)
+  (show-bug-report-information))
+
+(define %options
+  ;; Specifications of the command-line options.
+  (list (option '("verbose") #f #f
+                (lambda (opt name arg result)
+                  (alist-cons 'verbose? #t result)))
+        (option '("bootstrap") #f #f
+                (lambda (opt name arg result)
+                  (alist-cons 'bootstrap? #t result)))
+
+        (option '(#\h "help") #f #f
+                (lambda args
+                  (show-help)
+                  (exit 0)))
+        (option '(#\V "version") #f #f
+                (lambda args
+                  (show-version-and-exit "guix pull")))))
+
+(define (guix-pull . args)
+  (define (parse-options)
+    ;; Return the alist of option values.
+    (args-fold args %options
+               (lambda (opt name arg result)
+                 (leave (_ "~A: unrecognized option~%") name))
+               (lambda (arg result)
+                 (leave (_ "~A: unexpected argument~%") arg))
+               %default-options))
+
+  (let ((opts  (parse-options))
+        (store (open-connection)))
+    (with-error-handling
+      (let ((tarball (download-and-store store)))
+        (unless tarball
+          (leave (_ "failed to download up-to-date source, exiting\n")))
+        (parameterize ((%guile-for-build
+                        (package-derivation store
+                                            (if (assoc-ref opts 'bootstrap?)
+                                                %bootstrap-guile
+                                                guile-final)))
+                       (current-build-output-port
+                        (if (assoc-ref opts 'verbose?)
+                            (current-error-port)
+                            (%make-void-port "w"))))
+          (let*-values (((config-dir)
+                         (config-directory))
+                        ((source drv)
+                         (unpack store tarball))
+                        ((source-dir)
+                         (derivation-output-path
+                          (assoc-ref (derivation-outputs drv) "out"))))
+            (show-what-to-build store (list source))
+            (if (build-derivations store (list source))
+                (let ((latest (string-append config-dir "/latest")))
+                  (add-indirect-root store latest)
+                  (switch-symlinks latest source-dir)
+                  (format #t
+                          (_ "updated ~a successfully deployed under `~a'~%")
+                          %guix-package-name latest)
+                  #t))))))))

guix/ui.scm

@@ -41,6 +41,7 @@
             location->string
             call-with-temporary-output-file
             switch-symlinks
+            config-directory
             fill-paragraph
             string->recutils
             package->recutils
@@ -178,6 +179,26 @@ both when LINK already exists and when it does not."
     (symlink target pivot)
     (rename-file pivot link)))
 
+(define (config-directory)
+  "Return the name of the configuration directory, after making sure that it
+exists.  Honor the XDG specs,
+<http://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html>."
+  (let ((dir (and=> (or (getenv "XDG_CONFIG_HOME")
+                        (and=> (getenv "HOME")
+                               (cut string-append <> "/.config")))
+                    (cut string-append <> "/guix"))))
+    (catch 'system-error
+      (lambda ()
+        (mkdir dir)
+        dir)
+      (lambda args
+        (match (system-error-errno args)
+          ((or EEXIST 0)
+           dir)
+          (err
+           (leave (_ "failed to create configuration directory `~a': ~a~%")
+                  dir (strerror err))))))))
+
 (define* (fill-paragraph str width #:optional (column 0))
   "Fill STR such that each line contains at most WIDTH characters, assuming
 that the first character is at COLUMN.

po/POTFILES.in

@@ -8,4 +8,5 @@ guix/scripts/build.scm
 guix/scripts/download.scm
 guix/scripts/package.scm
 guix/scripts/gc.scm
+guix/scripts/pull.scm
 guix/ui.scm

scripts/guix.in

@@ -22,7 +22,8 @@
 ;; IMPORTANT: We must avoid loading any modules from Guix here,
 ;; because we need to adjust the guile load paths first.
 ;; It's okay to import modules from core Guile though.
-(use-modules (ice-9 regex))
+(use-modules (ice-9 regex)
+             (srfi srfi-26))
 
 (let ()
   (define-syntax-rule (push! elt v) (set! v (cons elt v)))
@@ -45,7 +46,14 @@
     (unless (getenv "GUIX_UNINSTALLED")
       (let ((module-dir (config-lookup "guilemoduledir")))
         (push! module-dir %load-path)
-        (push! module-dir %load-compiled-path))))
+        (push! module-dir %load-compiled-path))
+      (let ((updates-dir (and=> (or (getenv "XDG_CONFIG_HOME")
+                                    (and=> (getenv "HOME")
+                                           (cut string-append <> "/.config")))
+                                (cut string-append <> "/guix/latest"))))
+        (when (file-exists? updates-dir)
+          (push! updates-dir %load-path)
+          (push! updates-dir %load-compiled-path)))))
 
   (define (run-guix-main)
     (let ((guix-main (module-ref (resolve-interface '(guix ui))