gnu: Add net-base.

* gnu/packages/system.scm (net-base): New variable.

build-system/trivial: Take the 'source' field into account.

* guix/build-system/trivial.scm (trivial-build): When SOURCE is true,
  add it to INPUTS.
  (trivial-cross-build): Likewise.
* tests/packages.scm ("trivial with source"): New test.

gnu: vm: Set the default networking route.

* gnu/system/dmd.scm (static-networking-service): Add #:gateway
  parameter and honor it.
* gnu/system/vm.scm (system-qemu-image): Pass #:gateway to
  'static-networking-service'.

gnu: Add net-tools.

* gnu/packages/linux.scm (net-tools): New variable.

gnu: dmd: Download from alpha.gnu.org.

* gnu/packages/system.scm (dmd): Use the alpha.gnu.org URL.

gnu: harfbuzz: Update to 0.9.21.

* gnu/packages/gtk.scm (harfbuzz): Update to 0.9.21.

gnu: Add dvdisaster.

* gnu/packages/cdrom.scm (dvdisaster): New variable.

guix package: Add '--delete-generations'.

* guix/scripts/package.scm (switch-to-previous-generation): New function.
  (roll-back): Use the new function instead of 'switch-link'.
  (show-help): Add '--delete-generations'.
  (%options): Likewise.
  (guix-package)[process-actions]: Add 'current-generation-number',
  'display-and-delete', and 'delete-generation'.  Add support for
  '--delete-generations', and reindent the code.
* tests/guix-package.sh: Test '--delete-generations'.
* doc/guix.texi (Invoking guix-package): Document '--delete-generations'.

guix package: Add 'link-to-empty-profile'.

* guix/scripts/package.scm (link-to-empty-profile): New function.
  (roll-back): Use it.

guix package: Exit with 0 when there is nothing to list.

* guix/scripts/package.scm (guix-package)[process-query]: Exit with 0
  when there are no generations containing packages or no profiles.

gnu: xf86-input-joystick: Fix installation path.

* gnu/packages/xorg.scm (xf86-input-joystick): Fix installation path.

gnu: xf86-input-vmmouse: Fix installation path.

* gnu/packages/xorg.scm (xf86-input-vmmouse): Fix installation path.

gnu: xf86-input-synaptics: Fix installation paths.

* gnu/packages/xorg.scm (xf86-input-synaptics): Fix installation paths.

gnu: zile: Fix references to /bin/sh.

* gnu/packages/zile.scm (zile): Add 'patch-/bin/sh' phase.  Move Perl
  and help2man to 'native-inputs'.

gnu: vm: Add nscd service.

* gnu/system/dmd.scm (nscd-service): New procedure.
* gnu/system/vm.scm (system-qemu-image): Use it.  Make /var/run/nscd.

packages: Make the 'output' parameter of 'package-output' optional.

* guix/packages.scm (package-output): Make the 'output' parameter
  optional.

gnu: vm: Add 'networking' service.

* gnu/system/vm.scm (system-qemu-image): Use
  'static-networking-service'.  Add /etc/resolv.conf.  Add Inetutils to
  the profile.
* gnu/system/dmd.scm (static-networking-service): New procedure.

gnu: vm: Register the profile as a GC root.

* gnu/system/vm.scm (system-qemu-image): Register PROFILE as a GC root.

gnu: vm: Add 'host-name' service.

* gnu/system/dmd.scm (host-name-service): New procedure.
  (mingetty-service): Require the 'host-name' service.
* gnu/system/vm.scm (system-qemu-image): Add the 'host-name' service.
  Set PS1 in /etc/bashrc to something sensible.

gnu: vm: Add /etc/issue and a motd.

* gnu/system/vm.scm (system-qemu-image): Build a 'motd' and an 'issue'
  file.  Pass 'unix-pam-service' that motd.  Have /etc/issue point to
  the 'issue' file.