gnu: Add ncmpcpp.

* gnu/packages/mpd.scm (ncmpcpp): New variable.

Signed-off-by: Ludovic Courtès <ludo@gnu.org>

services: udev: Make sure modules are found, and use "udevadm settle".

* gnu/services/base.scm (udev-service): Set $LINUX_MODULE_DIRECTORY.  In
  the parent, invoke "udevadm settle" before "udevadm trigger".

system: Set $LINUX_MODULE_DIRECTORY as a function or /run/booted-system.

* gnu/system.scm (etc-directory): Remove #:kernel parameter.  Set
  LINUX_MODULE_DIRECTORY as a function or /run/booted-system.
  (operating-system-etc-directory): Update accordingly.

doc: Improve wording and example in "Using the Configuration System".

* doc/guix.texi (Using the Configuration System): Make the intro more
  user-oriented.  Change example to return an operating system.  Fix
  typos.  Mention mandatory/optional fields.

gnu: guix: Use the development version by default.

* gnu/packages/package-management.scm (guix): Rename to...
  (guix-0.6): ... this.
  (guix-devel): Rename to...
  (guix): ... this.  Replace references to 'guix' by references to
  'guix-0.6'.

gnu: guix: Add development version.

* gnu/packages/package-management.scm (guix-devel): New variable.

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.

gnu: Adjust for (gnu packages image) merger.

* gnu/packages/aidc.scm: Use (gnu packages image).

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.

gnu: Add talkfilters.

* gnu/packages/games.scm (talkfilters): New variable.

gnu: Add qrencode.

* gnu/packages/aidc.scm (qrencode): New variable.

gnu: Consolidate libjpeg, libpng, and libtiff into one module.

* gnu/packages/image.scm: New file.
* gnu-system.am (GNU_SYSTEM_MODULES): Add image.scm and remove libjpeg.scm,
  libpng.scm, and libtiff.scm.
* gnu/packages/libjpeg.scm, gnu/packages/libpng.scm, gnu/packages/libtiff.scm:
  Delete files.
* gnu/packages/emacs.scm gnu/packages/games.scm, gnu/packages/gd.scm,
  gnu/packages/geeqie.scm, gnu/packages/ghostscript.scm,
  gnu/packages/gimp.scm, gnu/packages/gnome.scm, gnu/packages/gnunet.scm,
  gnu/packages/gnustep.scm, gnu/packages/gnuzilla.scm,
  gnu/packages/graphviz.scm, gnu/packages/gtk.scm,
  gnu/packages/imagemagick.scm, gnu/packages/inkscape.scm,
  gnu/packages/netpbm.scm, gnu/packages/pdf.scm, gnu/packages/plotutils.scm,
  gnu/packages/qemu.scm, gnu/packages/qt.scm, gnu/packages/scheme.scm,
  gnu/packages/sdl.scm, gnu/packages/slim.scm, gnu/packages/tcl.scm,
  gnu/packages/texlive.scm, gnu/packages/video.scm, gnu/packages/xiph.scm,
  gnu/packages/xorg.scm: Use (gnu packages image) module.

gnu: Enable libvpx support in ffmpeg.

* gnu/packages/video.scm (ffmpeg): Add libvpx input.

system: Adjust the set of fields with default values.

* gnu/system.scm (<operating-system>)[file-systems]: Remove default.
  [locale]: Add default value.

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.

gnu: Add libsodium.

* gnu-system.am (GNU_SYSTEM_MODULES): Add crypto.scm.
* gnu/packages/crypto.scm: New file.

gnu: Add guile-opengl.

* gnu/packages/gl.scm (guile-opengl): New variable.