git-download: Support recursive clones.

* guix/git-download.scm (<git-reference>)[recursive?]: New field.
  (git-fetch): Add 'inputs' variable.  Add it to the #:inputs argument
  of 'build-expression->derivation'.  Augment builder with call to
  'set-path-environment-variable', and pass #:recursive? to
  'git-fetch'.
* guix/build/git.scm (git-fetch): Add #:recursive? parameter.  Pass
  --recursive when RECURSIVE? is true, and delete all the '.git' files.

system: Add a 'system?' field to user accounts.

* gnu/system/shadow.scm (<user-account>)[system?]: New field.
* gnu/system.scm (user-account->gexp): Add it.
* guix/build/activation.scm (add-user): Add #:system? parameter and
  honor it.
  (activate-users+groups): Handle the 'system?' part of user tuples.
  Pass it to 'add-user'.  Don't create PROFILE-DIR when SYSTEM? is
  true.
* gnu/services/dbus.scm (dbus-service): Add 'system?' field for
  "messagebus" account.
* gnu/services/base.scm (guix-build-accounts): Likewise.
* gnu/services/avahi.scm (avahi-service): Likewise.

system: Install /var/guix/profiles/system-1-link on new systems.

* guix/build/install.scm (directives): Add /var/guix/profiles/system.
  (populate-root-file-system): Add 'system' parameter.  Create
  /var/guix/profiles/system-1-link.
* guix/scripts/system.scm (install): Pass OS-DIR to
  'populate-root-file-system'.
* guix/build/vm.scm (initialize-root-partition): Add #:system-directory
  parameter, and pass it to 'populate-root-file-system'.
  (initialize-hard-disk): Add #:system-directory parameter, and pass it
  to 'initialize-root-partition'.
* gnu/system/vm.scm (qemu-image): Add #:os-derivation parameter and pass
  it to 'initialize-hard-disk'.
  (system-disk-image, system-qemu-image,
  system-qemu-image/shared-store): Pass #:os-derivation to 'qemu-image.

guix system: Add 'reconfigure' action.

* guix/scripts/system.scm (%system-profile): New variable.
  (switch-to-system, previous-grub-entries): New procedures.
  (unless-file-not-found): New macro.
  (show-help): Add 'reconfigure'.
  (guix-system): Handle it.
* gnu/system.scm: Export 'operating-system-activation-script'.
* doc/guix.texi (Invoking guix system): Document it.

activation: Preserve /etc/groups upon reboots.

This is a followup to e2fcc23.  The /etc/group file would be cleared
when booting.

* guix/build/activation.scm (activate-users+groups)[touch]: Rewrite so
  it does not wipe out FILE's contents.

guix {system,offload}: Improve reporting of syntax errors.

* guix/scripts/system.scm (read-operating-system) <catch handler>: Add
  case for 'syntax-error'.  Correct message for default case.
* guix/scripts/offload.scm (build-machines) <catch handler>: Add case
  for 'syntax-error'.
* tests/guix-system.sh: New file.
* Makefile.am (SH_TESTS): Add it.

guix system: Gracefully handle 'install-grub' errors.

* guix/scripts/system.scm (install): Wrap 'install-grub' call in
  'false-if-exception'.  This is a followup to 641f9a2a.

linux-initrd: Allow unionfs to have a large number of open files.

Fixes <http://bugs.gnu.org/17827>.

* guix/build/linux-initrd.scm (mount-root-file-system) [volatile-root?]:
  Pass unionfs '-o max_file=65536'.

Merge branch 'core-updates'

substitute-binary: Warn about uninitialized ACL.

* guix/scripts/substitute-binary.scm (guix-substitute-binary): Call
  'check-acl-initialized'.
  (check-acl-initialized): Don't rely on 'equal?' to compare keys.
  Instead, convert keys to strings.

guix system: 'init' makes sure the target store directory exists.

* guix/scripts/system.scm (install): Before calling 'copy-closure', make
  sure directory (%store-prefix) under TARGET exists.

substitute-binary: Avoid the term "narinfo" in user messages.

* guix/scripts/substitute-binary.scm (assert-valid-narinfo): Change
  message to avoid the term "narinfo".

Merge branch 'master' into core-updates

ui: Avoid circularity with (guix gexp).

Fixes a regression introduced in 56b8210 ("guix build: Allow gexps to be
passed to '-e'.")

* guix/ui.scm (%guix-user-module): Wrap in 'delay'.
  (read/eval): Adjust accordingly.

guix build: Allow gexps to be passed to '-e'.

* guix/ui.scm (%guix-user-module): New variable.
  (read/eval): Pass it as the second argument to 'eval'.
* guix/scripts/build.scm (options/resolve-packages): Add case for
  'gexp?'.
* tests/guix-build.sh: Add tests.
* doc/guix.texi (Invoking guix build): Document '-e gexp'.
guxi build: Allow gexps to be passed to '-e'.

* guix/ui.scm (%guix-user-module): New variable.
  (read/eval): Pass it as the second argument to 'eval'.
* guix/scripts/build.scm (options/resolve-packages): Add case for
  'gexp?'.
* tests/guix-build.sh: Add tests.
* doc/guix.texi (Invoking guix build): Document '-e gexp'.

Separate package description translations from string translations.

* po/packages/LINGUAS, po/packages/Makevars, po/packages/POTFILES.in:
  New files.
* po/guix/Makevars (DOMAIN): Change to "guix".
  (XGETTEXT_OPTIONS): Remove "--keyword=synopsis --keyword=description".
* po/guix/POTFILES.in: Remove gnu/packages/*.scm.
* configure.ac: Change to gettext 0.18.3.  Produce
  po/packages/Makefile.in.
* Makefile.am (SUBDIRS): Add po/packages.
* guix/ui.scm (%package-text-domain): New variable.
  (P_): New procedure.
  (package->recutils): Use 'P_' instead of '_'.
* guix/scripts/package.scm (find-packages-by-description): Use 'P_'
  instead of 'gettext'.

pull: Copy and compile gnu.scm.

* guix/build/pull.scm (build-guix): Copy gnu.scm to OUT.

guix build: Only 'guix build' sets #:print-build-trace.

This makes 'guix package' et al. slightly less verbose, by not emitting
"@ substituter-started" lines and similar.

* guix/scripts/build.scm (set-build-options-from-command-line): Pass
  #:print-build-trace.
  (%default-options): Add 'print-build-trace?'.

build-system/gnu: Add 'package-with-restricted-references'.

* guix/build-system/gnu.scm (package-with-restricted-references): New
  procedure.

Merge branch 'master' into core-updates