Merge branch 'master' into staging

18 files changed, 1230 insertions, 225 deletions

diff --git a/guix/build-system/cargo.scm b/guix/build-system/cargo.scm
index c637fbb162..4a1eb0cfa0 100644
--- a/guix/build-system/cargo.scm
+++ b/guix/build-system/cargo.scm
@@ -43,17 +43,11 @@
 to NAME and VERSION."
   (string-append crate-url name "/" version "/download"))
 
-(define (default-cargo)
-  "Return the default Cargo package."
+(define (default-rust)
+  "Return the default Rust package."
   ;; Lazily resolve the binding to avoid a circular dependency.
   (let ((rust (resolve-interface '(gnu packages rust))))
-    (module-ref rust 'cargo)))
-
-(define (default-rustc)
-  "Return the default Rustc package."
-  ;; Lazily resolve the binding to avoid a circular dependency.
-  (let ((rust (resolve-interface '(gnu packages rust))))
-    (module-ref rust 'rustc)))
+    (module-ref rust 'rust)))
 
 (define %cargo-build-system-modules
   ;; Build-side modules imported by default.
@@ -115,14 +109,13 @@ to NAME and VERSION."
 
 (define* (lower name
                 #:key source inputs native-inputs outputs system target
-                (cargo (default-cargo))
-                (rustc (default-rustc))
+                (rust (default-rust))
                 #:allow-other-keys
                 #:rest arguments)
   "Return a bag for NAME."
 
   (define private-keywords
-    '(#:source #:target #:cargo #:rustc #:inputs #:native-inputs #:outputs))
+    '(#:source #:target #:rust #:inputs #:native-inputs #:outputs))
 
   (and (not target) ;; TODO: support cross-compilation
        (bag
@@ -136,8 +129,8 @@ to NAME and VERSION."
 
                         ;; Keep the standard inputs of 'gnu-build-system'
                         ,@(standard-packages)))
-         (build-inputs `(("cargo" ,cargo)
-                         ("rustc" ,rustc)
+         (build-inputs `(("cargo" ,rust "cargo")
+                         ("rustc" ,rust)
                          ,@native-inputs))
          (outputs outputs)
          (build cargo-build)
diff --git a/guix/build/union.scm b/guix/build/union.scm
index d46b750035..1179f1234b 100644
--- a/guix/build/union.scm
+++ b/guix/build/union.scm
@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2012, 2013, 2014, 2016, 2017 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2012, 2013, 2014, 2016, 2017, 2018 Ludovic Courtès <ludo@gnu.org>
 ;;; Copyright © 2014 Mark H Weaver <mhw@netris.org>
 ;;; Copyright © 2017 Huang Ying <huang.ying.caritas@gmail.com>
 ;;;
@@ -25,7 +25,9 @@
   #:use-module (srfi srfi-26)
   #:use-module (rnrs bytevectors)
   #:use-module (rnrs io ports)
-  #:export (union-build))
+  #:export (union-build
+
+            warn-about-collision))
 
 ;;; Commentary:
 ;;;
@@ -76,14 +78,29 @@ identical, #f otherwise."
                                    (or (eof-object? n1)
                                        (loop))))))))))))))
 
+(define (warn-about-collision files)
+  "Handle the collision among FILES by emitting a warning and choosing the
+first one of THEM."
+  (format (current-error-port)
+          "~%warning: collision encountered:~%~{  ~a~%~}"
+          files)
+  (let ((file (first files)))
+    (format (current-error-port) "warning: choosing ~a~%" file)
+    file))
+
 (define* (union-build output inputs
                       #:key (log-port (current-error-port))
                       (create-all-directories? #f)
-                      (symlink symlink))
+                      (symlink symlink)
+                      (resolve-collision warn-about-collision))
   "Build in the OUTPUT directory a symlink tree that is the union of all the
 INPUTS, using SYMLINK to create symlinks.  As a special case, if
 CREATE-ALL-DIRECTORIES?, creates the subdirectories in the output directory to
-make sure the caller can modify them later."
+make sure the caller can modify them later.
+
+When two or more regular files collide, call RESOLVE-COLLISION with the list
+of colliding files and use the one that it returns; or, if RESOLVE-COLLISION
+returns #f, skip the faulty file altogether."
 
   (define (symlink* input output)
     (format log-port "`~a' ~~> `~a'~%" input output)
@@ -92,17 +109,10 @@ make sure the caller can modify them later."
   (define (resolve-collisions output dirs files)
     (cond ((null? dirs)
            ;; The inputs are all files.
-           (format (current-error-port)
-                   "~%warning: collision encountered:~%~{~a~%~}"
-                   files)
-
-           (let ((file (first files)))
-             ;; TODO: Implement smarter strategies.
-             (format (current-error-port)
-                     "warning: arbitrarily choosing ~a~%"
-                     file)
-
-             (symlink* file output)))
+           (match (resolve-collision files)
+             (#f #f)
+             ((? string? file)
+              (symlink* file output))))
 
           (else
            ;; The inputs are a mixture of files and directories
diff --git a/guix/ci.scm b/guix/ci.scm
new file mode 100644
index 0000000000..881f3d3927
--- /dev/null
+++ b/guix/ci.scm
@@ -0,0 +1,78 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2018 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 ci)
+  #:use-module (guix http-client)
+  #:autoload   (json parser) (json->scm)
+  #:use-module (srfi srfi-9)
+  #:export (build?
+            build-id
+            build-derivation
+            build-system
+            build-status
+            build-timestamp
+
+            %query-limit
+            queued-builds
+            latest-builds))
+
+;;; Commentary:
+;;;
+;;; This module provides a client to the HTTP interface of the Hydra and
+;;; Cuirass continuous integration (CI) tools.
+;;;
+;;; Code:
+
+(define-record-type <build>
+  (make-build id derivation system status timestamp)
+  build?
+  (id          build-id)                          ;integer
+  (derivation  build-derivation)                  ;string | #f
+  (system      build-system)                      ;string
+  (status      build-status)                      ;integer
+  (timestamp   build-timestamp))                  ;integer
+
+(define %query-limit
+  ;; Max number of builds requested in queries.
+  1000)
+
+(define (json-fetch url)
+  (let* ((port (http-fetch url))
+         (json (json->scm port)))
+    (close-port port)
+    json))
+
+(define (json->build json)
+  (make-build (hash-ref json "id")
+              (hash-ref json "derivation")
+              (hash-ref json "system")
+              (hash-ref json "buildstatus")
+              (hash-ref json "timestamp")))
+
+(define* (queued-builds url #:optional (limit %query-limit))
+  "Return the list of queued derivations on URL."
+  (let ((queue (json-fetch (string-append url "/api/queue?nr="
+                                          (number->string limit)))))
+    (map json->build queue)))
+
+(define* (latest-builds url #:optional (limit %query-limit))
+  (let ((latest (json-fetch (string-append url "/api/latestbuilds?nr="
+                                           (number->string limit)))))
+    ;; Note: Hydra does not provide a "derivation" field for entries in
+    ;; 'latestbuilds', but Cuirass does.
+    (map json->build latest)))
diff --git a/guix/discovery.scm b/guix/discovery.scm
index 7b57579023..2b627d108e 100644
--- a/guix/discovery.scm
+++ b/guix/discovery.scm
@@ -17,7 +17,7 @@
 ;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
 
 (define-module (guix discovery)
-  #:use-module (guix ui)
+  #:use-module (guix i18n)
   #:use-module (guix modules)
   #:use-module (guix combinators)
   #:use-module (guix build syscalls)
@@ -25,7 +25,8 @@
   #:use-module (ice-9 match)
   #:use-module (ice-9 vlist)
   #:use-module (ice-9 ftw)
-  #:export (scheme-modules
+  #:export (scheme-files
+            scheme-modules
             fold-modules
             all-modules
             fold-module-public-variables))
@@ -85,13 +86,18 @@ DIRECTORY is not accessible."
                 (lambda args
                   (let ((errno (system-error-errno args)))
                     (unless (= errno ENOENT)
-                      (warning (G_ "cannot access `~a': ~a~%")
-                               directory (strerror errno)))
+                      (format (current-error-port) ;XXX
+                              (G_ "cannot access `~a': ~a~%")
+                              directory (strerror errno)))
                     '())))))
 
-(define* (scheme-modules directory #:optional sub-directory)
+(define* (scheme-modules directory #:optional sub-directory
+                         #:key (warn (const #f)))
   "Return the list of Scheme modules available under DIRECTORY.
-Optionally, narrow the search to SUB-DIRECTORY."
+Optionally, narrow the search to SUB-DIRECTORY.
+
+WARN is called when a module could not be loaded.  It is passed the module
+name and the exception key and arguments."
   (define prefix-len
     (string-length directory))
 
@@ -103,31 +109,32 @@ Optionally, narrow the search to SUB-DIRECTORY."
                       (resolve-interface module))
                     (lambda args
                       ;; Report the error, but keep going.
-                      (warn-about-load-error module args)
+                      (warn module args)
                       #f))))
               (scheme-files (if sub-directory
                                 (string-append directory "/" sub-directory)
                                 directory))))
 
-(define (fold-modules proc init path)
+(define* (fold-modules proc init path #:key (warn (const #f)))
   "Fold over all the Scheme modules present in PATH, a list of directories.
 Call (PROC MODULE RESULT) for each module that is found."
   (fold (lambda (spec result)
           (match spec
             ((? string? directory)
-             (fold proc result (scheme-modules directory)))
+             (fold proc result (scheme-modules directory #:warn warn)))
             ((directory . sub-directory)
              (fold proc result
-                   (scheme-modules directory sub-directory)))))
+                   (scheme-modules directory sub-directory
+                                   #:warn warn)))))
         '()
         path))
 
-(define (all-modules path)
+(define* (all-modules path #:key (warn (const #f)))
   "Return the list of package modules found in PATH, a list of directories to
 search.  Entries in PATH can be directory names (strings) or (DIRECTORY
 . SUB-DIRECTORY) pairs, in which case modules are searched for beneath
 SUB-DIRECTORY."
-  (fold-modules cons '() path))
+  (fold-modules cons '() path #:warn warn))
 
 (define (fold-module-public-variables proc init modules)
   "Call (PROC OBJECT RESULT) for each variable exported by one of MODULES,
diff --git a/guix/docker.scm b/guix/docker.scm
index 060232148e..a75534c33b 100644
--- a/guix/docker.scm
+++ b/guix/docker.scm
@@ -1,6 +1,7 @@
 ;;; GNU Guix --- Functional package management for GNU
 ;;; Copyright © 2017 Ricardo Wurmus <rekado@elephly.net>
 ;;; Copyright © 2017 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2018 Chris Marusich <cmmarusich@gmail.com>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -23,9 +24,12 @@
   #:use-module ((guix build utils)
                 #:select (mkdir-p
                           delete-file-recursively
-                          with-directory-excursion))
-  #:use-module (guix build store-copy)
+                          with-directory-excursion
+                          invoke))
   #:use-module (srfi srfi-19)
+  #:use-module (srfi srfi-26)
+  #:use-module ((texinfo string-utils)
+                #:select (escape-special-chars))
   #:use-module (rnrs bytevectors)
   #:use-module (ice-9 match)
   #:export (build-docker-image))
@@ -33,8 +37,7 @@
 ;; Load Guile-JSON at run time to simplify the job of 'imported-modules' & co.
 (module-use! (current-module) (resolve-interface '(json)))
 
-;; Generate a 256-bit identifier in hexadecimal encoding for the Docker image
-;; containing the closure at PATH.
+;; Generate a 256-bit identifier in hexadecimal encoding for the Docker image.
 (define docker-id
   (compose bytevector->base16-string sha256 string->utf8))
 
@@ -102,82 +105,123 @@ return \"a\"."
     ((first rest ...)
      first)))
 
-(define* (build-docker-image image path
-                             #:key closure compressor
+(define* (build-docker-image image paths prefix
+                             #:key
                              (symlinks '())
+                             (transformations '())
                              (system (utsname:machine (uname)))
+                             compressor
                              (creation-time (current-time time-utc)))
-  "Write to IMAGE a Docker image archive from the given store PATH.  The image
-contains the closure of PATH, as specified in CLOSURE (a file produced by
-#:references-graphs).  SYMLINKS must be a list of (SOURCE -> TARGET) tuples
-describing symlinks to be created in the image, where each TARGET is relative
-to PATH.  SYSTEM is a GNU triplet (or prefix thereof) of the system the
-binaries at PATH are for; it is used to produce metadata in the image.
-
-Use COMPRESSOR, a command such as '(\"gzip\" \"-9n\"), to compress IMAGE.  Use
-CREATION-TIME, a SRFI-19 time-utc object, as the creation time in metadata."
-  (let ((directory "/tmp/docker-image")           ;temporary working directory
-        (closure (canonicalize-path closure))
-        (id (docker-id path))
-        (time (date->string (time-utc->date creation-time) "~4"))
-        (arch (let-syntax ((cond* (syntax-rules ()
-                                    ((_ (pattern clause) ...)
-                                     (cond ((string-prefix? pattern system)
-                                            clause)
-                                           ...
-                                           (else
-                                            (error "unsupported system"
-                                                   system)))))))
-                (cond* ("x86_64" "amd64")
-                       ("i686"   "386")
-                       ("arm"    "arm")
-                       ("mips64" "mips64le")))))
+  "Write to IMAGE a Docker image archive containing the given PATHS.  PREFIX
+must be a store path that is a prefix of any store paths in PATHS.
+
+SYMLINKS must be a list of (SOURCE -> TARGET) tuples describing symlinks to be
+created in the image, where each TARGET is relative to PREFIX.
+TRANSFORMATIONS must be a list of (OLD -> NEW) tuples describing how to
+transform the PATHS.  Any path in PATHS that begins with OLD will be rewritten
+in the Docker image so that it begins with NEW instead.  If a path is a
+non-empty directory, then its contents will be recursively added, as well.
+
+SYSTEM is a GNU triplet (or prefix thereof) of the system the binaries in
+PATHS are for; it is used to produce metadata in the image.  Use COMPRESSOR, a
+command such as '(\"gzip\" \"-9n\"), to compress IMAGE.  Use CREATION-TIME, a
+SRFI-19 time-utc object, as the creation time in metadata."
+  (define (sanitize path-fragment)
+    (escape-special-chars
+     ;; GNU tar strips the leading slash off of absolute paths before applying
+     ;; the transformations, so we need to do the same, or else our
+     ;; replacements won't match any paths.
+     (string-trim path-fragment #\/)
+     ;; Escape the basic regexp special characters (see: "(sed) BRE syntax").
+     ;; We also need to escape "/" because we use it as a delimiter.
+     "/*.^$[]\\"
+     #\\))
+  (define transformation->replacement
+    (match-lambda
+      ((old '-> new)
+       ;; See "(tar) transform" for details on the expression syntax.
+       (string-append "s/^" (sanitize old) "/" (sanitize new) "/"))))
+  (define (transformations->expression transformations)
+    (let ((replacements (map transformation->replacement transformations)))
+      (string-append
+       ;; Avoid transforming link targets, since that would break some links
+       ;; (e.g., symlinks that point to an absolute store path).
+       "flags=rSH;"
+       (string-join replacements ";")
+       ;; Some paths might still have a leading path delimiter even after tar
+       ;; transforms them (e.g., "/a/b" might be transformed into "/b"), so
+       ;; strip any leading path delimiters that remain.
+       ";s,^//*,,")))
+  (define transformation-options
+    (if (eq? '() transformations)
+        '()
+        `("--transform" ,(transformations->expression transformations))))
+  (let* ((directory "/tmp/docker-image") ;temporary working directory
+         (id (docker-id prefix))
+         (time (date->string (time-utc->date creation-time) "~4"))
+         (arch (let-syntax ((cond* (syntax-rules ()
+                                     ((_ (pattern clause) ...)
+                                      (cond ((string-prefix? pattern system)
+                                             clause)
+                                            ...
+                                            (else
+                                             (error "unsupported system"
+                                                    system)))))))
+                 (cond* ("x86_64" "amd64")
+                        ("i686"   "386")
+                        ("arm"    "arm")
+                        ("mips64" "mips64le")))))
     ;; Make sure we start with a fresh, empty working directory.
     (mkdir directory)
-
-    (and (with-directory-excursion directory
-           (mkdir id)
-           (with-directory-excursion id
-             (with-output-to-file "VERSION"
-               (lambda () (display schema-version)))
-             (with-output-to-file "json"
-               (lambda () (scm->json (image-description id time))))
-
-             ;; Wrap it up.
-             (let ((items (call-with-input-file closure
-                            read-reference-graph)))
-               ;; Create SYMLINKS.
-               (for-each (match-lambda
-                           ((source '-> target)
-                            (let ((source (string-trim source #\/)))
-                              (mkdir-p (dirname source))
-                              (symlink (string-append path "/" target)
-                                       source))))
-                         symlinks)
-
-               (and (zero? (apply system* "tar" "-cf" "layer.tar"
-                                  (append %tar-determinism-options
-                                          items
-                                          (map symlink-source symlinks))))
-                    (for-each delete-file-recursively
-                              (map (compose topmost-component symlink-source)
-                                   symlinks)))))
-
-           (with-output-to-file "config.json"
-             (lambda ()
-               (scm->json (config (string-append id "/layer.tar")
-                                  time arch))))
-           (with-output-to-file "manifest.json"
-             (lambda ()
-               (scm->json (manifest path id))))
-           (with-output-to-file "repositories"
-             (lambda ()
-               (scm->json (repositories path id)))))
-
-         (and (zero? (apply system* "tar" "-C" directory "-cf" image
-                            `(,@%tar-determinism-options
-                              ,@(if compressor
-                                    (list "-I" (string-join compressor))
-                                    '())
-                              ".")))
-              (begin (delete-file-recursively directory) #t)))))
+    (with-directory-excursion directory
+      (mkdir id)
+      (with-directory-excursion id
+        (with-output-to-file "VERSION"
+          (lambda () (display schema-version)))
+        (with-output-to-file "json"
+          (lambda () (scm->json (image-description id time))))
+
+        ;; Create SYMLINKS.
+        (for-each (match-lambda
+                    ((source '-> target)
+                     (let ((source (string-trim source #\/)))
+                       (mkdir-p (dirname source))
+                       (symlink (string-append prefix "/" target)
+                                source))))
+                  symlinks)
+
+        (apply invoke "tar" "-cf" "layer.tar"
+               `(,@transformation-options
+                 ,@%tar-determinism-options
+                 ,@paths
+                 ,@(map symlink-source symlinks)))
+        ;; It is possible for "/" to show up in the archive, especially when
+        ;; applying transformations.  For example, the transformation
+        ;; "s,^/a,," will (perhaps surprisingly) cause GNU tar to transform
+        ;; the path "/a" into "/".  The presence of "/" in the archive is
+        ;; probably benign, but it is definitely safe to remove it, so let's
+        ;; do that.  This fails when "/" is not in the archive, so use system*
+        ;; instead of invoke to avoid an exception in that case.
+        (system* "tar" "--delete" "/" "-f" "layer.tar")
+        (for-each delete-file-recursively
+                  (map (compose topmost-component symlink-source)
+                       symlinks)))
+
+      (with-output-to-file "config.json"
+        (lambda ()
+          (scm->json (config (string-append id "/layer.tar")
+                             time arch))))
+      (with-output-to-file "manifest.json"
+        (lambda ()
+          (scm->json (manifest prefix id))))
+      (with-output-to-file "repositories"
+        (lambda ()
+          (scm->json (repositories prefix id)))))
+
+    (apply invoke "tar" "-cf" image "-C" directory
+           `(,@%tar-determinism-options
+             ,@(if compressor
+                   (list "-I" (string-join compressor))
+                   '())
+             "."))
+    (delete-file-recursively directory)))
diff --git a/guix/gexp.scm b/guix/gexp.scm
index 8dea022e04..d26fad7e0b 100644
--- a/guix/gexp.scm
+++ b/guix/gexp.scm
@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2014, 2015, 2016, 2017 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2014, 2015, 2016, 2017, 2018 Ludovic Courtès <ludo@gnu.org>
 ;;; Copyright © 2018 Clément Lassieur <clement@lassieur.org>
 ;;;
 ;;; This file is part of GNU Guix.
@@ -60,6 +60,7 @@
             program-file-name
             program-file-gexp
             program-file-guile
+            program-file-module-path
 
             scheme-file
             scheme-file?
@@ -380,45 +381,49 @@ This is the declarative counterpart of 'gexp->derivation'."
          (apply gexp->derivation name gexp options)))))
 
 (define-record-type <program-file>
-  (%program-file name gexp guile)
+  (%program-file name gexp guile path)
   program-file?
   (name       program-file-name)                  ;string
   (gexp       program-file-gexp)                  ;gexp
-  (guile      program-file-guile))                ;package
+  (guile      program-file-guile)                 ;package
+  (path       program-file-module-path))          ;list of strings
 
-(define* (program-file name gexp #:key (guile #f))
+(define* (program-file name gexp #:key (guile #f) (module-path %load-path))
   "Return an object representing the executable store item NAME that runs
-GEXP.  GUILE is the Guile package used to execute that script.
+GEXP.  GUILE is the Guile package used to execute that script.  Imported
+modules of GEXP are looked up in MODULE-PATH.
 
 This is the declarative counterpart of 'gexp->script'."
-  (%program-file name gexp guile))
+  (%program-file name gexp guile module-path))
 
 (define-gexp-compiler (program-file-compiler (file <program-file>)
                                              system target)
   ;; Compile FILE by returning a derivation that builds the script.
   (match file
-    (($ <program-file> name gexp guile)
+    (($ <program-file> name gexp guile module-path)
      (gexp->script name gexp
+                   #:module-path module-path
                    #:guile (or guile (default-guile))))))
 
 (define-record-type <scheme-file>
-  (%scheme-file name gexp)
+  (%scheme-file name gexp splice?)
   scheme-file?
   (name       scheme-file-name)                  ;string
-  (gexp       scheme-file-gexp))                 ;gexp
+  (gexp       scheme-file-gexp)                  ;gexp
+  (splice?    scheme-file-splice?))              ;Boolean
 
-(define* (scheme-file name gexp)
+(define* (scheme-file name gexp #:key splice?)
   "Return an object representing the Scheme file NAME that contains GEXP.
 
 This is the declarative counterpart of 'gexp->file'."
-  (%scheme-file name gexp))
+  (%scheme-file name gexp splice?))
 
 (define-gexp-compiler (scheme-file-compiler (file <scheme-file>)
                                             system target)
   ;; Compile FILE by returning a derivation that builds the file.
   (match file
-    (($ <scheme-file> name gexp)
-     (gexp->file name gexp))))
+    (($ <scheme-file> name gexp splice?)
+     (gexp->file name gexp #:splice? splice?))))
 
 ;; Appending SUFFIX to BASE's output file name.
 (define-record-type <file-append>
@@ -1116,11 +1121,14 @@ they can refer to each other."
   (module-ref (resolve-interface '(gnu packages guile))
               'guile-2.2))
 
-(define (load-path-expression modules)
+(define* (load-path-expression modules #:optional (path %load-path))
   "Return as a monadic value a gexp that sets '%load-path' and
-'%load-compiled-path' to point to MODULES, a list of module names."
-  (mlet %store-monad ((modules  (imported-modules modules))
-                      (compiled (compiled-modules modules)))
+'%load-compiled-path' to point to MODULES, a list of module names.  MODULES
+are searched for in PATH."
+  (mlet %store-monad ((modules  (imported-modules modules
+                                                  #:module-path path))
+                      (compiled (compiled-modules modules
+                                                  #:module-path path)))
     (return (gexp (eval-when (expand load eval)
                     (set! %load-path
                       (cons (ungexp modules) %load-path))
@@ -1129,11 +1137,13 @@ they can refer to each other."
                             %load-compiled-path)))))))
 
 (define* (gexp->script name exp
-                       #:key (guile (default-guile)))
+                       #:key (guile (default-guile))
+                       (module-path %load-path))
   "Return an executable script NAME that runs EXP using GUILE, with EXP's
-imported modules in its search path."
+imported modules in its search path.  Look up EXP's modules in MODULE-PATH."
   (mlet %store-monad ((set-load-path
-                       (load-path-expression (gexp-modules exp))))
+                       (load-path-expression (gexp-modules exp)
+                                             module-path)))
     (gexp->derivation name
                       (gexp
                        (call-with-output-file (ungexp output)
@@ -1148,29 +1158,47 @@ imported modules in its search path."
 
                            (write '(ungexp set-load-path) port)
                            (write '(ungexp exp) port)
-                           (chmod port #o555)))))))
-
-(define* (gexp->file name exp #:key (set-load-path? #t))
-  "Return a derivation that builds a file NAME containing EXP.  When
-SET-LOAD-PATH? is true, emit code in the resulting file to set '%load-path'
-and '%load-compiled-path' to honor EXP's imported modules."
+                           (chmod port #o555))))
+                      #:module-path module-path)))
+
+(define* (gexp->file name exp #:key
+                     (set-load-path? #t)
+                     (module-path %load-path)
+                     (splice? #f))
+  "Return a derivation that builds a file NAME containing EXP.  When SPLICE?
+is true, EXP is considered to be a list of expressions that will be spliced in
+the resulting file.
+
+When SET-LOAD-PATH? is true, emit code in the resulting file to set
+'%load-path' and '%load-compiled-path' to honor EXP's imported modules.
+Lookup EXP's modules in MODULE-PATH."
   (match (if set-load-path? (gexp-modules exp) '())
     (()                                           ;zero modules
      (gexp->derivation name
                        (gexp
                         (call-with-output-file (ungexp output)
                           (lambda (port)
-                            (write '(ungexp exp) port))))
+                            (for-each (lambda (exp)
+                                        (write exp port))
+                                      '(ungexp (if splice?
+                                                   exp
+                                                   (gexp ((ungexp exp)))))))))
                        #:local-build? #t
                        #:substitutable? #f))
     ((modules ...)
-     (mlet %store-monad ((set-load-path (load-path-expression modules)))
+     (mlet %store-monad ((set-load-path (load-path-expression modules
+                                                              module-path)))
        (gexp->derivation name
                          (gexp
                           (call-with-output-file (ungexp output)
                             (lambda (port)
                               (write '(ungexp set-load-path) port)
-                              (write '(ungexp exp) port))))
+                              (for-each (lambda (exp)
+                                          (write exp port))
+                                        '(ungexp (if splice?
+                                                     exp
+                                                     (gexp ((ungexp exp)))))))))
+                         #:module-path module-path
                          #:local-build? #t
                          #:substitutable? #f)))))
 
@@ -1235,7 +1263,8 @@ This yields an 'etc' directory containing these two files."
                           files))))))
 
 (define* (directory-union name things
-                          #:key (copy? #f) (quiet? #f))
+                          #:key (copy? #f) (quiet? #f)
+                          (resolve-collision 'warn-about-collision))
   "Return a directory that is the union of THINGS, where THINGS is a list of
 file-like objects denoting directories.  For example:
 
@@ -1243,6 +1272,10 @@ file-like objects denoting directories.  For example:
 
 yields a directory that is the union of the 'guile' and 'emacs' packages.
 
+Call RESOLVE-COLLISION when several files collide, passing it the list of
+colliding files.  RESOLVE-COLLISION must return the chosen file or #f, in
+which case the colliding entry is skipped altogether.
+
 When HARD-LINKS? is true, create hard links instead of symlinks.  When QUIET?
 is true, the derivation will not print anything."
   (define symlink
@@ -1266,12 +1299,16 @@ is true, the derivation will not print anything."
      (computed-file name
                     (with-imported-modules '((guix build union))
                       (gexp (begin
-                              (use-modules (guix build union))
+                              (use-modules (guix build union)
+                                           (srfi srfi-1)) ;for 'first' and 'last'
+
                               (union-build (ungexp output)
                                            '(ungexp things)
 
                                            #:log-port (ungexp log-port)
-                                           #:symlink (ungexp symlink)))))))))
+                                           #:symlink (ungexp symlink)
+                                           #:resolve-collision
+                                           (ungexp resolve-collision)))))))))
 
 
 ;;;
diff --git a/guix/git.scm b/guix/git.scm
index d31c35f64f..9e89cc0062 100644
--- a/guix/git.scm
+++ b/guix/git.scm
@@ -28,9 +28,11 @@
   #:use-module (rnrs bytevectors)
   #:use-module (ice-9 match)
   #:use-module (srfi srfi-1)
+  #:use-module (srfi srfi-11)
   #:use-module (srfi srfi-34)
   #:use-module (srfi srfi-35)
   #:export (%repository-cache-directory
+            update-cached-checkout
             latest-repository-commit))
 
 (define %repository-cache-directory
@@ -68,11 +70,6 @@ make sure no empty directory is left behind."
     (lambda _
       (false-if-exception (rmdir directory)))))
 
-(define (repository->head-sha1 repo)
-  "Return the sha1 of the HEAD commit in REPOSITORY as a string."
-  (let ((oid (reference-target (repository-head repo))))
-    (oid->string (commit-id (commit-lookup repo oid)))))
-
 (define (url+commit->name url sha1)
   "Return the string \"<REPO-NAME>-<SHA1:7>\" where REPO-NAME is the name of
 the git repository, extracted from URL and SHA1:7 the seven first digits
@@ -82,21 +79,9 @@ of SHA1 string."
     (last (string-split url #\/)) ".git" "")
    "-" (string-take sha1 7)))
 
-(define* (copy-to-store store cache-directory #:key url repository)
-  "Copy CACHE-DIRECTORY recursively to STORE.  URL and REPOSITORY are used to
-create the store directory name."
-  (define (dot-git? file stat)
-    (and (string=? (basename file) ".git")
-         (eq? 'directory (stat:type stat))))
-
-  (let* ((commit (repository->head-sha1 repository))
-         (name   (url+commit->name url commit)))
-    (values (add-to-store store name #t "sha256" cache-directory
-                          #:select? (negate dot-git?))
-            commit)))
-
 (define (switch-to-ref repository ref)
-  "Switch to REPOSITORY's branch, commit or tag specified by REF."
+  "Switch to REPOSITORY's branch, commit or tag specified by REF.  Return the
+OID (roughly the commit hash) corresponding to REF."
   (define obj
     (match ref
       (('branch . branch)
@@ -122,7 +107,38 @@ create the store directory name."
                                        (string-append "refs/tags/" tag))))
          (object-lookup repository oid)))))
 
-  (reset repository obj RESET_HARD))
+  (reset repository obj RESET_HARD)
+  (object-id obj))
+
+(define* (update-cached-checkout url
+                                 #:key
+                                 (ref '(branch . "origin/master"))
+                                 (cache-directory
+                                  (%repository-cache-directory)))
+  "Update the cached checkout of URL to REF in CACHE-DIRECTORY.  Return two
+values: the cache directory name, and the SHA1 commit (a string) corresponding
+to REF.
+
+REF is pair whose key is [branch | commit | tag] and value the associated
+data, respectively [<branch name> | <sha1> | <tag name>]."
+  (with-libgit2
+   (let* ((cache-dir     (url-cache-directory url cache-directory))
+          (cache-exists? (openable-repository? cache-dir))
+          (repository    (if cache-exists?
+                             (repository-open cache-dir)
+                             (clone* url cache-dir))))
+     ;; Only fetch remote if it has not been cloned just before.
+     (when cache-exists?
+       (remote-fetch (remote-lookup repository "origin")))
+     (let ((oid (switch-to-ref repository ref)))
+
+       ;; Reclaim file descriptors and memory mappings associated with
+       ;; REPOSITORY as soon as possible.
+       (when (module-defined? (resolve-interface '(git repository))
+                              'repository-close!)
+         (repository-close! repository))
+
+       (values cache-dir (oid->string oid))))))
 
 (define* (latest-repository-commit store url
                                    #:key
@@ -137,16 +153,16 @@ data, respectively [<branch name> | <sha1> | <tag name>].
 
 Git repositories are kept in the cache directory specified by
 %repository-cache-directory parameter."
-  (with-libgit2
-   (let* ((cache-dir     (url-cache-directory url cache-directory))
-          (cache-exists? (openable-repository? cache-dir))
-          (repository    (if cache-exists?
-                             (repository-open cache-dir)
-                             (clone* url cache-dir))))
-     ;; Only fetch remote if it has not been cloned just before.
-     (when cache-exists?
-       (remote-fetch (remote-lookup repository "origin")))
-     (switch-to-ref repository ref)
-     (copy-to-store store cache-dir
-                    #:url url
-                    #:repository repository))))
+  (define (dot-git? file stat)
+    (and (string=? (basename file) ".git")
+         (eq? 'directory (stat:type stat))))
+
+  (let*-values (((checkout commit)
+                 (update-cached-checkout url
+                                         #:ref ref
+                                         #:cache-directory cache-directory))
+                ((name)
+                 (url+commit->name url commit)))
+    (values (add-to-store store name #t "sha256" checkout
+                          #:select? (negate dot-git?))
+            commit)))
diff --git a/guix/modules.scm b/guix/modules.scm
index 6c602eda48..65928f67f2 100644
--- a/guix/modules.scm
+++ b/guix/modules.scm
@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2016, 2017 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2016, 2017, 2018 Ludovic Courtès <ludo@gnu.org>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -25,10 +25,12 @@
   #:use-module (ice-9 match)
   #:export (missing-dependency-error?
             missing-dependency-module
+            missing-dependency-search-path
 
             file-name->module-name
             module-name->file-name
 
+            source-module-dependencies
             source-module-closure
             live-module-closure
             guix-module-name?))
@@ -46,7 +48,8 @@
 ;; The error corresponding to a missing module.
 (define-condition-type &missing-dependency-error &error
   missing-dependency-error?
-  (module  missing-dependency-module))
+  (module      missing-dependency-module)
+  (search-path missing-dependency-search-path))
 
 (define (colon-symbol? obj)
   "Return true if OBJ is a symbol that starts with a colon."
@@ -131,7 +134,8 @@ depends on."
          (module-file-dependencies file))
         (#f
          (raise (condition (&missing-dependency-error
-                            (module module))))))))
+                            (module module)
+                            (search-path load-path))))))))
 
 (define* (module-closure modules
                          #:key
diff --git a/guix/scripts/build.scm b/guix/scripts/build.scm
index 57f2d82c5c..401087e830 100644
--- a/guix/scripts/build.scm
+++ b/guix/scripts/build.scm
@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2012, 2013, 2014, 2015, 2016, 2017 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2012, 2013, 2014, 2015, 2016, 2017, 2018 Ludovic Courtès <ludo@gnu.org>
 ;;; Copyright © 2013 Mark H Weaver <mhw@netris.org>
 ;;;
 ;;; This file is part of GNU Guix.
@@ -69,13 +69,21 @@
 found.  Return #f if no build log was found."
   (define (valid-url? url)
     ;; Probe URL and return #t if it is accessible.
-    (catch 'getaddrinfo-error
+    (catch #t
       (lambda ()
         (guard (c ((http-get-error? c) #f))
           (close-port (http-fetch url #:buffered? #f))
           #t))
-      (lambda _
-        #f)))
+      (match-lambda*
+        (('getaddrinfo-error . _)
+         #f)
+        (('tls-certificate-error args ...)
+         (report-error (G_ "cannot access build log at '~a':~%") url)
+         (print-exception (current-error-port) #f
+                          'tls-certificate-error args)
+         (exit 1))
+        ((key . args)
+         (apply throw key args)))))
 
   (define (find-url file)
     (let ((base (basename file)))
diff --git a/guix/scripts/environment.scm b/guix/scripts/environment.scm
index 4f88c513c0..f8a9702b30 100644
--- a/guix/scripts/environment.scm
+++ b/guix/scripts/environment.scm
@@ -332,7 +332,7 @@ packages."
                   (let ((module (make-user-module '())))
                     (packages->outputs (load* file module) mode)))
                  (('manifest . file)
-                  (let ((module (make-user-module '())))
+                  (let ((module (make-user-module '((guix profiles) (gnu)))))
                     (manifest->outputs (load* file module))))
                  (_ '(#f)))
                opts)))
diff --git a/guix/scripts/gc.scm b/guix/scripts/gc.scm
index a31d2236b0..e4ed7227ff 100644
--- a/guix/scripts/gc.scm
+++ b/guix/scripts/gc.scm
@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2012, 2013, 2015, 2016, 2017 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2012, 2013, 2015, 2016, 2017, 2018 Ludovic Courtès <ludo@gnu.org>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -61,6 +61,8 @@ Invoke the garbage collector.\n"))
   -R, --requisites       list the requisites of PATHS"))
   (display (G_ "
       --referrers        list the referrers of PATHS"))
+  (display (G_ "
+      --derivers         list the derivers of PATHS"))
   (newline)
   (display (G_ "
       --verify[=OPTS]    verify the integrity of the store; OPTS is a
@@ -153,6 +155,10 @@ Invoke the garbage collector.\n"))
                 (lambda (opt name arg result)
                   (alist-cons 'action 'list-referrers
                               (alist-delete 'action result))))
+        (option '("derivers") #f #f
+                (lambda (opt name arg result)
+                  (alist-cons 'action 'list-derivers
+                              (alist-delete 'action result))))
         (option '("list-failures") #f #f
                 (lambda (opt name arg result)
                   (alist-cons 'action 'list-failures
@@ -241,6 +247,8 @@ Invoke the garbage collector.\n"))
                            (requisites store (list item)))))
         ((list-referrers)
          (list-relatives referrers))
+        ((list-derivers)
+         (list-relatives valid-derivers))
         ((optimize)
          (assert-no-extra-arguments)
          (optimize-store store))
diff --git a/guix/scripts/graph.scm b/guix/scripts/graph.scm
index 78f09f181b..346ca4ea88 100644
--- a/guix/scripts/graph.scm
+++ b/guix/scripts/graph.scm
@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2015, 2016, 2017 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2015, 2016, 2017, 2018 Ludovic Courtès <ludo@gnu.org>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -27,9 +27,11 @@
   #:use-module (guix gexp)
   #:use-module (guix derivations)
   #:use-module (guix memoization)
+  #:use-module (guix modules)
   #:use-module ((guix build-system gnu) #:select (standard-packages))
   #:use-module (gnu packages)
   #:use-module (guix sets)
+  #:use-module ((guix utils) #:select (location-file))
   #:use-module (srfi srfi-1)
   #:use-module (srfi srfi-26)
   #:use-module (srfi srfi-34)
@@ -44,6 +46,7 @@
             %derivation-node-type
             %reference-node-type
             %referrer-node-type
+            %module-node-type
             %node-types
 
             guix-graph))
@@ -332,6 +335,36 @@ substitutes."
 
 
 ;;;
+;;; Scheme modules.
+;;;
+
+(define (module-from-package package)
+  (file-name->module-name (location-file (package-location package))))
+
+(define (source-module-dependencies* module)
+  "Like 'source-module-dependencies' but filter out modules that are not
+package modules, while attempting to retain user package modules."
+  (remove (match-lambda
+            (('guix _ ...) #t)
+            (('system _ ...) #t)
+            (('language _ ...) #t)
+            (('ice-9 _ ...) #t)
+            (('srfi _ ...) #t)
+            (_ #f))
+          (source-module-dependencies module)))
+
+(define %module-node-type
+  ;; Show the graph of package modules.
+  (node-type
+   (name "module")
+   (description "the graph of package modules")
+   (convert (lift1 (compose list module-from-package) %store-monad))
+   (identifier (lift1 identity %store-monad))
+   (label object->string)
+   (edges (lift1 source-module-dependencies* %store-monad))))
+
+
+;;;
 ;;; List of node types.
 ;;;
 
@@ -344,7 +377,8 @@ substitutes."
         %bag-emerged-node-type
         %derivation-node-type
         %reference-node-type
-        %referrer-node-type))
+        %referrer-node-type
+        %module-node-type))
 
 (define (lookup-node-type name)
   "Return the node type called NAME.  Raise an error if it is not found."
diff --git a/guix/scripts/pack.scm b/guix/scripts/pack.scm
index 59dd117edb..488638adc5 100644
--- a/guix/scripts/pack.scm
+++ b/guix/scripts/pack.scm
@@ -3,6 +3,7 @@
 ;;; Copyright © 2017 Efraim Flashner <efraim@flashner.co.il>
 ;;; Copyright © 2017 Ricardo Wurmus <rekado@elephly.net>
 ;;; Copyright © 2018 Konrad Hinsen <konrad.hinsen@fastmail.net>
+;;; Copyright © 2018 Chris Marusich <cmmarusich@gmail.com>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -33,7 +34,9 @@
   #:use-module (guix derivations)
   #:use-module (guix scripts build)
   #:use-module (gnu packages)
+  #:use-module (gnu packages bootstrap)
   #:use-module (gnu packages compression)
+  #:use-module (gnu packages guile)
   #:autoload   (gnu packages base) (tar)
   #:autoload   (gnu packages package-management) (guix)
   #:autoload   (gnu packages gnupg) (libgcrypt)
@@ -67,6 +70,11 @@
                     #~(#+(file-append bzip2 "/bin/bzip2") "-9"))
         (compressor "none" "" #f)))
 
+;; This one is only for use in this module, so don't put it in %compressors.
+(define bootstrap-xz
+  (compressor "bootstrap-xz" ".xz"
+              #~(#+(file-append %bootstrap-coreutils&co "/bin/xz") "-e -T0")))
+
 (define (lookup-compressor name)
   "Return the compressor object called NAME.  Error out if it could not be
 found."
@@ -230,6 +238,7 @@ the image."
   (define build
     (with-imported-modules `(,@(source-module-closure '((guix docker))
                                                       #:select? not-config?)
+                             (guix build store-copy)
                              ((guix config) => ,config))
       #~(begin
           ;; Guile-JSON is required by (guix docker).
@@ -237,13 +246,15 @@ the image."
            (string-append #+json "/share/guile/site/"
                           (effective-version)))
 
-          (use-modules (guix docker) (srfi srfi-19))
+          (use-modules (guix docker) (srfi srfi-19) (guix build store-copy))
 
           (setenv "PATH" (string-append #$tar "/bin"))
 
-          (build-docker-image #$output #$profile
+          (build-docker-image #$output
+                              (call-with-input-file "profile"
+                                read-reference-graph)
+                              #$profile
                               #:system (or #$target (utsname:machine (uname)))
-                              #:closure "profile"
                               #:symlinks '#$symlinks
                               #:compressor '#$(compressor-command compressor)
                               #:creation-time (make-time time-utc 0 1)))))
@@ -325,6 +336,9 @@ the image."
          (option '("localstatedir") #f #f
                  (lambda (opt name arg result)
                    (alist-cons 'localstatedir? #t result)))
+         (option '("bootstrap") #f #f
+                 (lambda (opt name arg result)
+                   (alist-cons 'bootstrap? #t result)))
 
          (append %transformation-options
                  %standard-build-options)))
@@ -352,6 +366,8 @@ Create a bundle of PACKAGE.\n"))
   -m, --manifest=FILE    create a pack with the manifest from FILE"))
   (display (G_ "
       --localstatedir    include /var/guix in the resulting pack"))
+  (display (G_ "
+      --bootstrap        use the bootstrap binaries to build the pack"))
   (newline)
   (display (G_ "
   -h, --help             display this help and exit"))
@@ -393,28 +409,43 @@ Create a bundle of PACKAGE.\n"))
        (else (packages->manifest packages)))))
 
   (with-error-handling
-    (parameterize ((%graft? (assoc-ref opts 'graft?)))
-      (let* ((dry-run?    (assoc-ref opts 'dry-run?))
-             (manifest    (manifest-from-args opts))
-             (pack-format (assoc-ref opts 'format))
-             (name        (string-append (symbol->string pack-format)
-                                         "-pack"))
-             (target      (assoc-ref opts 'target))
-             (compressor  (assoc-ref opts 'compressor))
-             (symlinks    (assoc-ref opts 'symlinks))
-             (build-image (match (assq-ref %formats pack-format)
-                            ((? procedure? proc) proc)
-                            (#f
-                             (leave (G_ "~a: unknown pack format")
-                                    format))))
-             (localstatedir? (assoc-ref opts 'localstatedir?)))
-        (with-store store
+    (let* ((dry-run?    (assoc-ref opts 'dry-run?))
+           (manifest    (manifest-from-args opts))
+           (pack-format (assoc-ref opts 'format))
+           (name        (string-append (symbol->string pack-format)
+                                       "-pack"))
+           (target      (assoc-ref opts 'target))
+           (bootstrap?  (assoc-ref opts 'bootstrap?))
+           (compressor  (if bootstrap?
+                            bootstrap-xz
+                            (assoc-ref opts 'compressor)))
+           (tar         (if bootstrap?
+                            %bootstrap-coreutils&co
+                            tar))
+           (symlinks    (assoc-ref opts 'symlinks))
+           (build-image (match (assq-ref %formats pack-format)
+                          ((? procedure? proc) proc)
+                          (#f
+                           (leave (G_ "~a: unknown pack format")
+                                  format))))
+           (localstatedir? (assoc-ref opts 'localstatedir?)))
+      (with-store store
+        (parameterize ((%graft? (assoc-ref opts 'graft?))
+                       (%guile-for-build (package-derivation
+                                          store
+                                          (if (assoc-ref opts 'bootstrap?)
+                                              %bootstrap-guile
+                                              (canonical-package guile-2.2)))))
           ;; Set the build options before we do anything else.
           (set-build-options-from-command-line store opts)
 
           (run-with-store store
             (mlet* %store-monad ((profile (profile-derivation
                                            manifest
+                                           #:hooks (if bootstrap?
+                                                       '()
+                                                       %default-profile-hooks)
+                                           #:locales? (not bootstrap?)
                                            #:target target))
                                  (drv (build-image name profile
                                                    #:target
@@ -424,7 +455,9 @@ Create a bundle of PACKAGE.\n"))
                                                    #:symlinks
                                                    symlinks
                                                    #:localstatedir?
-                                                   localstatedir?)))
+                                                   localstatedir?
+                                                   #:tar
+                                                   tar)))
               (mbegin %store-monad
                 (show-what-to-build* (list drv)
                                      #:use-substitutes?
diff --git a/guix/scripts/package.scm b/guix/scripts/package.scm
index d8b80efe8e..4f519e6f33 100644
--- a/guix/scripts/package.scm
+++ b/guix/scripts/package.scm
@@ -194,15 +194,18 @@ denote ranges as interpreted by 'matching-generations'."
 
 (define* (build-and-use-profile store profile manifest
                                 #:key
+                                allow-collisions?
                                 bootstrap? use-substitutes?
                                 dry-run?)
   "Build a new generation of PROFILE, a file name, using the packages
-specified in MANIFEST, a manifest object."
+specified in MANIFEST, a manifest object.  When ALLOW-COLLISIONS? is true,
+do not treat collisions in MANIFEST as an error."
   (when (equal? profile %current-profile)
     (ensure-default-profile))
 
   (let* ((prof-drv (run-with-store store
                      (profile-derivation manifest
+                                         #:allow-collisions? allow-collisions?
                                          #:hooks (if bootstrap?
                                                      '()
                                                      %default-profile-hooks)
@@ -408,6 +411,8 @@ Install, remove, or upgrade packages in a single transaction.\n"))
   -p, --profile=PROFILE  use PROFILE instead of the user's default profile"))
   (newline)
   (display (G_ "
+      --allow-collisions do not treat collisions in the profile as an error"))
+  (display (G_ "
       --bootstrap        use the bootstrap Guile to build the profile"))
   (display (G_ "
       --verbose          produce verbose output"))
@@ -544,6 +549,10 @@ kind of search path~%")
                  (lambda (opt name arg result arg-handler)
                    (values (alist-cons 'verbose? #t result)
                            #f)))
+         (option '("allow-collisions") #f #f
+                 (lambda (opt name arg result arg-handler)
+                   (values (alist-cons 'allow-collisions? #t result)
+                           #f)))
          (option '(#\s "search") #t #f
                  (lambda (opt name arg result arg-handler)
                    (values (cons `(query search ,(or arg ""))
@@ -831,13 +840,15 @@ processed, #f otherwise."
   (let* ((user-module  (make-user-module '((guix profiles) (gnu))))
          (manifest     (load* file user-module))
          (bootstrap?   (assoc-ref opts 'bootstrap?))
-         (substitutes? (assoc-ref opts 'substitutes?)))
+         (substitutes? (assoc-ref opts 'substitutes?))
+         (allow-collisions? (assoc-ref opts 'allow-collisions?)))
     (if dry-run?
         (format #t (G_ "would install new manifest from '~a' with ~d entries~%")
                 file (length (manifest-entries manifest)))
         (format #t (G_ "installing new manifest from '~a' with ~d entries~%")
                 file (length (manifest-entries manifest))))
     (build-and-use-profile store profile manifest
+                           #:allow-collisions? allow-collisions?
                            #:bootstrap? bootstrap?
                            #:use-substitutes? substitutes?
                            #:dry-run? dry-run?)))
@@ -856,6 +867,7 @@ processed, #f otherwise."
   (define dry-run? (assoc-ref opts 'dry-run?))
   (define bootstrap? (assoc-ref opts 'bootstrap?))
   (define substitutes? (assoc-ref opts 'substitutes?))
+  (define allow-collisions? (assoc-ref opts 'allow-collisions?))
   (define profile  (or (assoc-ref opts 'profile) %current-profile))
   (define transform (options->transformation opts))
 
@@ -894,6 +906,7 @@ processed, #f otherwise."
       (show-manifest-transaction store manifest step3
                                  #:dry-run? dry-run?)
       (build-and-use-profile store profile new
+                             #:allow-collisions? allow-collisions?
                              #:bootstrap? bootstrap?
                              #:use-substitutes? substitutes?
                              #:dry-run? dry-run?))))
diff --git a/guix/scripts/system.scm b/guix/scripts/system.scm
index f0c4a2ba1b..b50cabcd1a 100644
--- a/guix/scripts/system.scm
+++ b/guix/scripts/system.scm
@@ -1,7 +1,7 @@
 ;;; GNU Guix --- Functional package management for GNU
 ;;; Copyright © 2014, 2015, 2016, 2017, 2018 Ludovic Courtès <ludo@gnu.org>
 ;;; Copyright © 2016 Alex Kost <alezost@gmail.com>
-;;; Copyright © 2016, 2017 Chris Marusich <cmmarusich@gmail.com>
+;;; Copyright © 2016, 2017, 2018 Chris Marusich <cmmarusich@gmail.com>
 ;;; Copyright © 2017 Mathieu Othacehe <m.othacehe@gmail.com>
 ;;;
 ;;; This file is part of GNU Guix.
@@ -701,7 +701,9 @@ checking this by themselves in their 'check' procedure."
                                  ("iso9660" "image.iso")
                                  (_         "disk-image"))
                         #:disk-image-size image-size
-                        #:file-system-type file-system-type))))
+                        #:file-system-type file-system-type))
+    ((docker-image)
+     (system-docker-image os #:register-closures? #t))))
 
 (define (maybe-suggest-running-guix-pull)
   "Suggest running 'guix pull' if this has never been done before."
@@ -905,6 +907,8 @@ Some ACTIONS support additional ARGS.\n"))
   (display (G_ "\
    disk-image       build a disk image, suitable for a USB stick\n"))
   (display (G_ "\
+   docker-image     build a Docker image\n"))
+  (display (G_ "\
    init             initialize a root file system to run GNU\n"))
   (display (G_ "\
    extension-graph  emit the service extension graph in Dot format\n"))
@@ -1142,7 +1146,7 @@ argument list and OPTS is the option alist."
           (case action
             ((build container vm vm-image disk-image reconfigure init
               extension-graph shepherd-graph list-generations roll-back
-              switch-generation search)
+              switch-generation search docker-image)
              (alist-cons 'action action result))
             (else (leave (G_ "~a: unknown action~%") action))))))
 
@@ -1171,7 +1175,7 @@ argument list and OPTS is the option alist."
         (exit 1))
 
       (case action
-        ((build container vm vm-image disk-image reconfigure)
+        ((build container vm vm-image disk-image docker-image reconfigure)
          (unless (or (= count 1)
                      (and expr (= count 0)))
            (fail)))
diff --git a/guix/scripts/weather.scm b/guix/scripts/weather.scm
index 2e782e36ce..5c934abaef 100644
--- a/guix/scripts/weather.scm
+++ b/guix/scripts/weather.scm
@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2017 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2017, 2018 Ludovic Courtès <ludo@gnu.org>
 ;;; Copyright © 2017 Ricardo Wurmus <rekado@elephly.net>
 ;;;
 ;;; This file is part of GNU Guix.
@@ -29,11 +29,14 @@
   #:use-module (guix grafts)
   #:use-module ((guix build syscalls) #:select (terminal-columns))
   #:use-module (guix scripts substitute)
+  #:use-module (guix http-client)
+  #:use-module (guix ci)
   #:use-module (gnu packages)
   #:use-module (web uri)
   #:use-module (srfi srfi-1)
   #:use-module (srfi srfi-19)
   #:use-module (srfi srfi-26)
+  #:use-module (srfi srfi-34)
   #:use-module (srfi srfi-37)
   #:use-module (ice-9 match)
   #:use-module (ice-9 format)
@@ -100,6 +103,57 @@ values."
 (define-syntax-rule (let/time ((time result exp)) body ...)
   (call-with-time (lambda () exp) (lambda (time result) body ...)))
 
+(define (histogram field proc seed lst)
+  "Return an alist giving a histogram of all the values of FIELD for elements
+of LST. FIELD must be a one element procedure that returns a field's value.
+For each FIELD value, call PROC with the previous field-specific result.
+Example:
+
+  (histogram car (lambda (x n) (+ 1 n)) 0 '((a . x)(b . y)(a . z)))
+  => ((a . 2) (b . 1))
+
+meaning that we have two a's and one b."
+  (let loop ((lst lst)
+             (result '()))
+    (match lst
+      (()
+       result)
+      ((head . tail)
+       (let ((value (field head)))
+         (loop tail
+               (match (assoc-ref result value)
+                 (#f
+                  `((,value . ,(proc head seed)) ,@result))
+                 (previous
+                  `((,value . ,(proc head previous))
+                    ,@(alist-delete value result))))))))))
+
+(define (throughput lst timestamp)
+  "Return the throughput, in items per second, given the elements of LST,
+calling TIMESTAMP to get the \"timestamp\" of each item."
+  (let ((oldest (reduce min +inf.0 (map build-timestamp lst)))
+        (now    (time-second (current-time time-utc))))
+    (/ (length lst) (- now oldest) 1.)))
+
+(define (queued-subset queue items)
+  "Return the subset of ITEMS, a list of store file names, that appears in
+QUEUE, a list of builds.  Return #f if elements in QUEUE lack information
+about the derivations queued, as is the case with Hydra."
+  (define queued
+    (append-map (lambda (build)
+                  (match (false-if-exception
+                          (read-derivation-from-file (build-derivation build)))
+                    (#f
+                     '())
+                    (drv
+                     (match (derivation->output-paths drv)
+                       (((names . items) ...) items)))))
+                queue))
+
+  (if (any (negate build-derivation) queue)
+      #f                                          ;no derivation information
+      (lset-intersection string=? queued items)))
+
 (define (report-server-coverage server items)
   "Report the subset of ITEMS available as substitutes on SERVER."
   (define MiB (* (expt 2 20) 1.))
@@ -111,6 +165,8 @@ values."
     (format #t "~a~%" server)
     (let ((obtained  (length narinfos))
           (requested (length items))
+          (missing   (lset-difference string=?
+                                      items (map narinfo-path narinfos)))
           (sizes     (filter-map narinfo-file-size narinfos))
           (time      (+ (time-second time)
                         (/ (time-nanosecond time) 1e9))))
@@ -131,7 +187,56 @@ values."
       (format #t (G_ "  ~,3h seconds per request (~,1h seconds in total)~%")
               (/ time requested 1.) time)
       (format #t (G_ "  ~,1h requests per second~%")
-              (/ requested time 1.)))))
+              (/ requested time 1.))
+
+      (guard (c ((http-get-error? c)
+                 (if (= 404 (http-get-error-code c))
+                     (format (current-error-port)
+                             (G_ "  (continuous integration information \
+unavailable)~%"))
+                     (format (current-error-port)
+                             (G_ "  '~a' returned ~a (~s)~%")
+                             (uri->string (http-get-error-uri c))
+                             (http-get-error-code c)
+                             (http-get-error-reason c)))))
+        (let* ((max    %query-limit)
+               (queue  (queued-builds server max))
+               (len    (length queue))
+               (histo  (histogram build-system
+                                  (lambda (build count)
+                                    (+ 1 count))
+                                  0 queue)))
+          (newline)
+          (unless (null? missing)
+            (let ((missing (length missing)))
+              (match (queued-subset queue missing)
+                (#f #f)
+                ((= length queued)
+                 (format #t (G_ "  ~,1f% (~h out of ~h) of the missing items \
+are queued~%")
+                         (* 100. (/ queued missing))
+                         queued missing)))))
+
+          (if (>= len max)
+              (format #t (G_ "  at least ~h queued builds~%") len)
+              (format #t (G_ "  ~h queued builds~%") len))
+          (for-each (match-lambda
+                      ((system . count)
+                       (format #t (G_ "      ~a: ~a (~0,1f%)~%")
+                               system count (* 100. (/ count len)))))
+                    histo))
+
+        (let* ((latest     (latest-builds server))
+               (builds/sec (throughput latest build-timestamp)))
+          (format #t (G_ "  build rate: ~1,2f builds per hour~%")
+                  (* builds/sec 3600.))
+          (for-each (match-lambda
+                      ((system . builds)
+                       (format #t (G_ "      ~a: ~,2f builds per hour~%")
+                               system
+                               (* (throughput builds build-timestamp)
+                                  3600.))))
+                    (histogram build-system cons '() latest)))))))
 
 
 ;;;
diff --git a/guix/self.scm b/guix/self.scm
new file mode 100644
index 0000000000..6220efb397
--- /dev/null
+++ b/guix/self.scm
@@ -0,0 +1,610 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2017, 2018 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 self)
+  #:use-module (guix config)
+  #:use-module (guix i18n)
+  #:use-module (guix modules)
+  #:use-module (guix gexp)
+  #:use-module (guix store)
+  #:use-module (guix monads)
+  #:use-module (guix discovery)
+  #:use-module (guix packages)
+  #:use-module (guix sets)
+  #:use-module (guix utils)
+  #:use-module (guix modules)
+  #:use-module (guix build utils)
+  #:use-module ((guix build compile) #:select (%lightweight-optimizations))
+  #:use-module (srfi srfi-1)
+  #:use-module (srfi srfi-9)
+  #:use-module (ice-9 match)
+  #:export (make-config.scm
+            compiled-guix
+            guix-derivation
+            reload-guix))
+
+
+;;;
+;;; Dependency handling.
+;;;
+
+(define* (false-if-wrong-guile package
+                               #:optional (guile-version (effective-version)))
+  "Return #f if PACKAGE depends on the \"wrong\" major version of Guile (e.g.,
+2.0 instead of 2.2), otherwise return PACKAGE."
+  (let ((guile (any (match-lambda
+                      ((label (? package? dep) _ ...)
+                       (and (string=? (package-name dep) "guile")
+                            dep)))
+                    (package-direct-inputs package))))
+    (and (or (not guile)
+             (string-prefix? guile-version
+                             (package-version guile)))
+         package)))
+
+(define (package-for-guile guile-version . names)
+  "Return the package with one of the given NAMES that depends on
+GUILE-VERSION (\"2.0\" or \"2.2\"), or #f if none of the packages matches."
+  (let loop ((names names))
+    (match names
+      (()
+       #f)
+      ((name rest ...)
+       (match (specification->package name)
+         (#f
+          (loop rest))
+         ((? package? package)
+          (or (false-if-wrong-guile package guile-version)
+              (loop rest))))))))
+
+(define specification->package
+  ;; Use our own variant of that procedure because that of (gnu packages)
+  ;; would traverse all the .scm files, which is wasteful.
+  (let ((ref (lambda (module variable)
+               (module-ref (resolve-interface module) variable))))
+    (match-lambda
+      ("guile"      (ref '(gnu packages commencement) 'guile-final))
+      ("guile-json" (ref '(gnu packages guile) 'guile-json))
+      ("guile-ssh"  (ref '(gnu packages ssh)   'guile-ssh))
+      ("guile-git"  (ref '(gnu packages guile) 'guile-git))
+      ("libgcrypt"  (ref '(gnu packages gnupg) 'libgcrypt))
+      ("zlib"       (ref '(gnu packages compression) 'zlib))
+      ("gzip"       (ref '(gnu packages compression) 'gzip))
+      ("bzip2"      (ref '(gnu packages compression) 'bzip2))
+      ("xz"         (ref '(gnu packages compression) 'xz))
+      ("guix"       (ref '(gnu packages package-management)
+                         'guix-register))
+      ("guile2.0-json" (ref '(gnu packages guile) 'guile2.0-json))
+      ("guile2.0-ssh"  (ref '(gnu packages ssh) 'guile2.0-ssh))
+      ("guile2.0-git"  (ref '(gnu packages guile) 'guile2.0-git))
+      (_               #f))))                     ;no such package
+
+
+;;;
+;;; Derivations.
+;;;
+
+;; Node in a DAG of build tasks.  Each node maps to a derivation, but it's
+;; easier to express things this way.
+(define-record-type <node>
+  (node name modules source dependencies compiled)
+  node?
+  (name          node-name)                       ;string
+  (modules       node-modules)                    ;list of module names
+  (source        node-source)                     ;list of source files
+  (dependencies  node-dependencies)               ;list of nodes
+  (compiled      node-compiled))                  ;node -> lowerable object
+
+(define (node-fold proc init nodes)
+  (let loop ((nodes nodes)
+             (visited (setq))
+             (result init))
+    (match nodes
+      (() result)
+      ((head tail ...)
+       (if (set-contains? visited head)
+           (loop tail visited result)
+           (loop tail (set-insert head visited)
+                 (proc head result)))))))
+
+(define (node-modules/recursive nodes)
+  (node-fold (lambda (node modules)
+               (append (node-modules node) modules))
+             '()
+             nodes))
+
+(define* (closure modules #:optional (except '()))
+  (source-module-closure modules
+                         #:select?
+                         (match-lambda
+                           (('guix 'config)
+                            #f)
+                           ((and module
+                                 (or ('guix _ ...) ('gnu _ ...)))
+                            (not (member module except)))
+                           (rest #f))))
+
+(define module->import
+  ;; Return a file-name/file-like object pair for the specified module and
+  ;; suitable for 'imported-files'.
+  (match-lambda
+    ((module '=> thing)
+     (let ((file (module-name->file-name module)))
+       (list file thing)))
+    (module
+        (let ((file (module-name->file-name module)))
+          (list file
+                (local-file (search-path %load-path file)))))))
+
+(define* (scheme-node name modules #:optional (dependencies '())
+                      #:key (extra-modules '()) (extra-files '())
+                      (extensions '())
+                      parallel? guile-for-build)
+  "Return a node that builds the given Scheme MODULES, and depends on
+DEPENDENCIES (a list of nodes).  EXTRA-MODULES is a list of additional modules
+added to the source, and EXTRA-FILES is a list of additional files.
+EXTENSIONS is a set of full-blown Guile packages (e.g., 'guile-json') that
+must be present in the search path."
+  (let* ((modules (append extra-modules
+                          (closure modules
+                                   (node-modules/recursive dependencies))))
+         (module-files (map module->import modules))
+         (source (imported-files (string-append name "-source")
+                                 (append module-files extra-files))))
+    (node name modules source dependencies
+          (compiled-modules name source modules
+                            (map node-source dependencies)
+                            (map node-compiled dependencies)
+                            #:extensions extensions
+                            #:parallel? parallel?
+                            #:guile-for-build guile-for-build))))
+
+(define (file-imports directory sub-directory pred)
+  "List all the files matching PRED under DIRECTORY/SUB-DIRECTORY.  Return a
+list of file-name/file-like objects suitable as inputs to 'imported-files'."
+  (map (lambda (file)
+         (list (string-drop file (+ 1 (string-length directory)))
+               (local-file file #:recursive? #t)))
+       (find-files (string-append directory "/" sub-directory) pred)))
+
+(define (scheme-modules* directory sub-directory)
+  "Return the list of module names found under SUB-DIRECTORY in DIRECTORY."
+  (let ((prefix (string-length directory)))
+    (map (lambda (file)
+           (file-name->module-name (string-drop file prefix)))
+         (scheme-files (string-append directory "/" sub-directory)))))
+
+(define* (compiled-guix source #:key (version %guix-version)
+                        (name (string-append "guix-" version))
+                        (guile-version (effective-version))
+                        (guile-for-build (guile-for-build guile-version))
+                        (libgcrypt (specification->package "libgcrypt"))
+                        (zlib (specification->package "zlib"))
+                        (gzip (specification->package "gzip"))
+                        (bzip2 (specification->package "bzip2"))
+                        (xz (specification->package "xz"))
+                        (guix (specification->package "guix")))
+  "Return a file-like object that contains a compiled Guix."
+  (define guile-json
+    (package-for-guile guile-version
+                       "guile-json"
+                       "guile2.0-json"))
+
+  (define guile-ssh
+    (package-for-guile guile-version
+                       "guile-ssh"
+                       "guile2.0-ssh"))
+
+  (define guile-git
+    (package-for-guile guile-version
+                       "guile-git"
+                       "guile2.0-git"))
+
+
+  (define dependencies
+    (match (append-map (lambda (package)
+                         (cons (list "x" package)
+                               (package-transitive-inputs package)))
+                       (list guile-git guile-json guile-ssh))
+      (((labels packages _ ...) ...)
+       packages)))
+
+  (define *core-modules*
+    (scheme-node "guix-core"
+                 '((guix)
+                   (guix monad-repl)
+                   (guix packages)
+                   (guix download)
+                   (guix discovery)
+                   (guix profiles)
+                   (guix build-system gnu)
+                   (guix build-system trivial)
+                   (guix build profiles)
+                   (guix build gnu-build-system))
+
+                 ;; Provide a dummy (guix config) with the default version
+                 ;; number, storedir, etc.  This is so that "guix-core" is the
+                 ;; same across all installations and doesn't need to be
+                 ;; rebuilt when the version changes, which in turn means we
+                 ;; can have substitutes for it.
+                 #:extra-modules
+                 `(((guix config)
+                    => ,(make-config.scm #:libgcrypt
+                                         (specification->package
+                                          "libgcrypt"))))
+
+                 #:guile-for-build guile-for-build))
+
+  (define *extra-modules*
+    (scheme-node "guix-extra"
+                 (filter-map (match-lambda
+                               (('guix 'scripts _ ..1) #f)
+                               (name name))
+                             (scheme-modules* source "guix"))
+                 (list *core-modules*)
+                 #:extensions dependencies
+                 #:guile-for-build guile-for-build))
+
+  (define *package-modules*
+    (scheme-node "guix-packages"
+                 `((gnu packages)
+                   ,@(scheme-modules* source "gnu/packages"))
+                 (list *core-modules* *extra-modules*)
+                 #:extensions dependencies
+                 #:extra-files                    ;all the non-Scheme files
+                 (file-imports source "gnu/packages"
+                               (lambda (file stat)
+                                 (and (eq? 'regular (stat:type stat))
+                                      (not (string-suffix? ".scm" file))
+                                      (not (string-suffix? ".go" file))
+                                      (not (string-prefix? ".#" file))
+                                      (not (string-suffix? "~" file)))))
+                 #:guile-for-build guile-for-build))
+
+  (define *system-modules*
+    (scheme-node "guix-system"
+                 `((gnu system)
+                   (gnu services)
+                   ,@(scheme-modules* source "gnu/system")
+                   ,@(scheme-modules* source "gnu/services"))
+                 (list *package-modules* *extra-modules* *core-modules*)
+                 #:extensions dependencies
+                 #:extra-files
+                 (file-imports source "gnu/system/examples" (const #t))
+                 #:guile-for-build
+                 guile-for-build))
+
+  (define *cli-modules*
+    (scheme-node "guix-cli"
+                 (scheme-modules* source "/guix/scripts")
+                 (list *core-modules* *extra-modules* *package-modules*
+                       *system-modules*)
+                 #:extensions dependencies
+                 #:guile-for-build guile-for-build))
+
+  (define *config*
+    (scheme-node "guix-config"
+                 '()
+                 #:extra-modules
+                 `(((guix config)
+                    => ,(make-config.scm #:libgcrypt libgcrypt
+                                         #:zlib zlib
+                                         #:gzip gzip
+                                         #:bzip2 bzip2
+                                         #:xz xz
+                                         #:guix guix
+                                         #:package-name
+                                         %guix-package-name
+                                         #:package-version
+                                         version
+                                         #:bug-report-address
+                                         %guix-bug-report-address
+                                         #:home-page-url
+                                         %guix-home-page-url)))
+                 #:guile-for-build guile-for-build))
+
+  (directory-union name
+                   (append-map (lambda (node)
+                                 (list (node-source node)
+                                       (node-compiled node)))
+
+                               ;; Note: *CONFIG* comes first so that it
+                               ;; overrides the (guix config) module that
+                               ;; comes with *CORE-MODULES*.
+                               (list *config*
+                                     *cli-modules*
+                                     *system-modules*
+                                     *package-modules*
+                                     *extra-modules*
+                                     *core-modules*))
+
+                   ;; Silently choose the first entry upon collision so that
+                   ;; we choose *CONFIG*.
+                   #:resolve-collision 'first
+
+                   ;; When we do (add-to-store "utils.scm"), "utils.scm" must
+                   ;; be a regular file, not a symlink.  Thus, arrange so that
+                   ;; regular files appear as regular files in the final
+                   ;; output.
+                   #:copy? #t
+                   #:quiet? #t))
+
+
+;;;
+;;; Generating (guix config).
+;;;
+
+(define %dependency-variables
+  ;; (guix config) variables corresponding to dependencies.
+  '(%libgcrypt %libz %xz %gzip %bzip2 %nix-instantiate
+    %sbindir %guix-register-program))
+
+(define %persona-variables
+  ;; (guix config) variables that define Guix's persona.
+  '(%guix-package-name
+    %guix-version
+    %guix-bug-report-address
+    %guix-home-page-url))
+
+(define %config-variables
+  ;; (guix config) variables corresponding to Guix configuration (storedir,
+  ;; localstatedir, etc.)
+  (sort (filter pair?
+                (module-map (lambda (name var)
+                              (and (not (memq name %dependency-variables))
+                                   (not (memq name %persona-variables))
+                                   (cons name (variable-ref var))))
+                            (resolve-interface '(guix config))))
+        (lambda (name+value1 name+value2)
+          (string<? (symbol->string (car name+value1))
+                    (symbol->string (car name+value2))))))
+
+(define* (make-config.scm #:key libgcrypt zlib gzip xz bzip2 guix
+                          (package-name "GNU Guix")
+                          (package-version "0")
+                          (bug-report-address "bug-guix@gnu.org")
+                          (home-page-url "https://gnu.org/s/guix"))
+
+  ;; Hack so that Geiser is not confused.
+  (define defmod 'define-module)
+
+  (scheme-file "config.scm"
+               #~(;; The following expressions get spliced.
+                   (#$defmod (guix config)
+                     #:export (%guix-package-name
+                               %guix-version
+                               %guix-bug-report-address
+                               %guix-home-page-url
+                               %sbindir
+                               %guix-register-program
+                               %libgcrypt
+                               %libz
+                               %gzip
+                               %bzip2
+                               %xz
+                               %nix-instantiate))
+
+                   #$@(map (match-lambda
+                             ((name . value)
+                              #~(define-public #$name #$value)))
+                           %config-variables)
+
+                   (define %guix-package-name #$package-name)
+                   (define %guix-version #$package-version)
+                   (define %guix-bug-report-address #$bug-report-address)
+                   (define %guix-home-page-url #$home-page-url)
+
+                   (define %sbindir
+                     ;; This is used to define '%guix-register-program'.
+                     ;; TODO: Use a derivation that builds nothing but the
+                     ;; C++ part.
+                     #+(and guix (file-append guix "/sbin")))
+
+                   (define %guix-register-program
+                     (or (getenv "GUIX_REGISTER")
+                         (and %sbindir
+                              (string-append %sbindir "/guix-register"))))
+
+                   (define %gzip
+                     #+(and gzip (file-append gzip "/bin/gzip")))
+                   (define %bzip2
+                     #+(and bzip2 (file-append bzip2 "/bin/bzip2")))
+                   (define %xz
+                     #+(and xz (file-append xz "/bin/xz")))
+
+                   (define %libgcrypt
+                     #+(and libgcrypt
+                            (file-append libgcrypt "/lib/libgcrypt")))
+                   (define %libz
+                     #+(and zlib
+                            (file-append zlib "/lib/libz")))
+
+                   (define %nix-instantiate       ;for (guix import snix)
+                     "nix-instantiate"))
+
+               ;; Guile 2.0 *requires* the 'define-module' to be at the
+               ;; top-level or it 'toplevel-ref' in the resulting .go file are
+               ;; made relative to a nonexistent anonymous module.
+               #:splice? #t))
+
+
+
+;;;
+;;; Building.
+;;;
+
+(define (imported-files name files)
+  ;; This is a non-monadic, simplified version of 'imported-files' from (guix
+  ;; gexp).
+  (define build
+    (with-imported-modules (source-module-closure
+                            '((guix build utils)))
+      #~(begin
+          (use-modules (ice-9 match)
+                       (guix build utils))
+
+          (mkdir (ungexp output)) (chdir (ungexp output))
+          (for-each (match-lambda
+                      ((final-path store-path)
+                       (mkdir-p (dirname final-path))
+
+                       ;; Note: We need regular files to be regular files, not
+                       ;; symlinks, as this makes a difference for
+                       ;; 'add-to-store'.
+                       (copy-file store-path final-path)))
+                    '#$files))))
+
+  ;; We're just copying files around, no need to substitute or offload it.
+  (computed-file name build
+                 #:options '(#:local-build? #t
+                             #:substitutable? #f)))
+
+(define* (compiled-modules name module-tree modules
+                           #:optional
+                           (dependencies '())
+                           (dependencies-compiled '())
+                           #:key
+                           (extensions '())       ;full-blown Guile packages
+                           parallel?
+                           guile-for-build)
+  ;; This is a non-monadic, enhanced version of 'compiled-file' from (guix
+  ;; gexp).
+  (define build
+    (with-imported-modules (source-module-closure
+                            '((guix build compile)
+                              (guix build utils)))
+      #~(begin
+          (use-modules (srfi srfi-26)
+                       (ice-9 match)
+                       (ice-9 format)
+                       (ice-9 threads)
+                       (guix build compile)
+                       (guix build utils))
+
+          (define (regular? file)
+            (not (member file '("." ".."))))
+
+          (define (report-load file total completed)
+            (display #\cr)
+            (format #t
+                    "loading...\t~5,1f% of ~d files" ;FIXME: i18n
+                    (* 100. (/ completed total)) total)
+            (force-output))
+
+          (define (report-compilation file total completed)
+            (display #\cr)
+            (format #t "compiling...\t~5,1f% of ~d files" ;FIXME: i18n
+                    (* 100. (/ completed total)) total)
+            (force-output))
+
+          (define (process-directory directory output)
+            (let ((files  (find-files directory "\\.scm$"))
+                  (prefix (+ 1 (string-length directory))))
+              ;; Hide compilation warnings.
+              (parameterize ((current-warning-port (%make-void-port "w")))
+                (compile-files directory #$output
+                               (map (cut string-drop <> prefix) files)
+                               #:workers (parallel-job-count)
+                               #:report-load report-load
+                               #:report-compilation report-compilation))))
+
+          (setvbuf (current-output-port) _IONBF)
+          (setvbuf (current-error-port) _IONBF)
+
+          (set! %load-path (cons #+module-tree %load-path))
+          (set! %load-path
+            (append '#+dependencies
+                    (map (lambda (extension)
+                           (string-append extension "/share/guile/site/"
+                                          (effective-version)))
+                         '#+extensions)
+                    %load-path))
+
+          (set! %load-compiled-path
+            (append '#+dependencies-compiled
+                    (map (lambda (extension)
+                           (string-append extension "/lib/guile/"
+                                          (effective-version)
+                                          "/site-ccache"))
+                         '#+extensions)
+                    %load-compiled-path))
+
+          ;; Load the compiler modules upfront.
+          (compile #f)
+
+          (mkdir #$output)
+          (chdir #+module-tree)
+          (process-directory "." #$output)
+          (newline))))
+
+  (computed-file name build
+                 #:guile guile-for-build
+                 #:options
+                 `(#:local-build? #f              ;allow substitutes
+
+                   ;; Don't annoy people about _IONBF deprecation.
+                   #:env-vars (("GUILE_WARN_DEPRECATED" . "no")))))
+
+
+;;;
+;;; Building.
+;;;
+
+(define (guile-for-build version)
+  "Return a derivation for Guile 2.0 or 2.2, whichever matches the currently
+running Guile."
+  (define canonical-package                       ;soft reference
+    (module-ref (resolve-interface '(gnu packages base))
+                'canonical-package))
+
+  (match version
+    ("2.2.2"
+     ;; Gross hack to avoid ABI incompatibilities (see
+     ;; <https://bugs.gnu.org/29570>.)
+     (module-ref (resolve-interface '(gnu packages guile))
+                 'guile-2.2.2))
+    ("2.2"
+     (canonical-package (module-ref (resolve-interface '(gnu packages guile))
+                                    'guile-2.2/fixed)))
+    ("2.0"
+     (module-ref (resolve-interface '(gnu packages guile))
+                 'guile-2.0))))
+
+(define* (guix-derivation source version
+                          #:optional (guile-version (effective-version)))
+  "Return, as a monadic value, the derivation to build the Guix from SOURCE
+for GUILE-VERSION.  Use VERSION as the version string."
+  (define (shorten version)
+    (if (and (string-every char-set:hex-digit version)
+             (> (string-length version) 9))
+        (string-take version 9)                   ;Git commit
+        version))
+
+  (define guile
+    (guile-for-build guile-version))
+
+  (mbegin %store-monad
+    (set-guile-for-build guile)
+    (lower-object (compiled-guix source
+                                 #:version version
+                                 #:name (string-append "guix-"
+                                                       (shorten version))
+                                 #:guile-version (match guile-version
+                                                   ("2.2.2" "2.2")
+                                                   (version version))
+                                 #:guile-for-build guile))))
diff --git a/guix/upstream.scm b/guix/upstream.scm
index caaa0e44e4..9e1056f7a7 100644
--- a/guix/upstream.scm
+++ b/guix/upstream.scm
@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2018 Ludovic Courtès <ludo@gnu.org>
 ;;; Copyright © 2015 Alex Kost <alezost@gmail.com>
 ;;;
 ;;; This file is part of GNU Guix.
@@ -153,7 +153,8 @@ correspond to the same version."
   (cons (resolve-interface '(guix gnu-maintenance))
         (all-modules (map (lambda (entry)
                             `(,entry . "guix/import"))
-                          %load-path))))
+                          %load-path)
+                     #:warn warn-about-load-error)))
 
 (define %updaters
   ;; The list of publically-known updaters.