hydra: Pass the directory name of the Nix checkout.

* build-aux/hydra/guix.scm (hydra-jobs): Extract the 'file-name' item
  from NIX-CHECKOUT, and pass that to 'tarball-package'.

hydra: Fix typo.

* build-aux/hydra/guix.scm (tarball-package): Unquote 'nix-checkout'.

hydra: Add missing import.

* build-aux/hydra/gnu-system.scm, build-aux/hydra/guix.scm: Use (guix
  derivations).

hydra: Return the .drv file names, not the <derivation> objects.

* build-aux/hydra/gnu-system.scm (package->alist): Call
  'derivation-file-name' on the result of 'package-derivation'.
* build-aux/hydra/guix.scm (package->alist): Likewise.

hydra: Point the Git submodule to our local copy.

* build-aux/hydra/guix.scm (tarball-package): Add 'nix-checkout'
  parameter.  Replace 'patch-bootstrap-script' phase by
  'set-nix-module'.
  (hydra-jobs): Get the 'nix' value from ARGUMENTS, and pass it to
  'tarball-package'.

derivations: 'derivation' and related procedures return a single value.

* guix/derivations.scm (derivation->output-path,
  derivation->output-paths): New procedures.
  (derivation-path->output-path): Use 'derivation->output-path'.
  (derivation-path->output-paths): Use 'derivation->output-paths'.
  (derivation): Accept 'derivation?' objects as inputs.  Return a single
  value.
  (build-derivations): New procedure.
  (compiled-modules): Use 'derivation->output-paths'.
  (build-expression->derivation)[source-path]: Add case for when the
  input matches 'derivation?'.
  [prologue]: Accept 'derivation?' objects in INPUTS.
  [mod-dir, go-dir]: Use 'derivation->output-path'.
* guix/download.scm (url-fetch): Adjust to the single-value return.
* guix/packages.scm (package-output): Use 'derivation->output-path'.
* guix/scripts/build.scm (guix-build): When the argument is
  'derivation-path?', pass it through 'read-derivation'.
  Use 'derivation-file-name' to print out the .drv file names, and to
  register them.  Use 'derivation->output-path' instead of
  'derivation-path->output-path'.
* guix/scripts/package.scm (roll-back): Adjust to the single-value
  return.
  (guix-package): Use 'derivation->output-path'.
* guix/ui.scm (show-what-to-build): Adjust to deal with 'derivation?'
  objects instead of .drv file names.
* gnu/system/grub.scm (grub-configuration-file): Use
  'derivation->output-path' instead of 'derivation-path->output-path'.
* gnu/system/vm.scm (qemu-image, system-qemu-image): Likewise.
* tests/builders.scm, tests/derivations.scm, tests/packages.scm,
  tests/store.scm, tests/union.scm: Adjust to the new calling
  convention.
* doc/guix.texi (Defining Packages, The Store, Derivations): Adjust
  accordingly.

tests: Clarify filtering of the "debug" output.

* tests/guix-package.sh: Clearly filter out the "debug" output of
  'gnu-make-boot0'.

derivations: Add a nicer printer.

* guix/derivations.scm (<derivation>): Add a printer.

derivations: Keep the .drv file name in <derivation> objects.

* guix/derivations.scm (<derivation>): Add 'file-name' field.
  (%read-derivation): Use (port-filename DRV-PORT) as the file name for
  the result.
  (derivation): Set the 'file-name' field in the result.
* tests/derivations.scm ("build derivation with 1 source"): Assert that
  'derivation-file-name' returns the right thing.

gnu: dbus: Add dependency on libX11.

* gnu/packages/glib.scm: Use #:export instead of 'define-public'.
  (dbus): Add LIBX11 as an input.

Merge branch 'python'

substitute-binary: Add '--help'.

Reported by Nikita Karetnikov <nikita@karetnikov.org>.

* guix/scripts/substitute-binary.scm (show-help): New procedure.
  (guix-substitute-binary): Add '--help'.

gnu: gnutls: Upgrade to 3.2.4.

* gnu/packages/gnutls.scm (gnutls): Update to 3.2.4; remove 'arguments'
  field, remove "patch/fix-tests" from the inputs.
* gnu/packages/patches/gnutls-fix-tests-on-32-bits-system.patch: Remove.
* gnu-system.am (dist_patch_DATA): Adjust accordingly.

gnu: Add python2-mechanize.

* gnu/packages/python.scm (python2-mechanize): New variable.

guix package: Rename generation-related procedures.

* guix/scripts/package.scm (profile-numbers): Rename to 'generation-numbers'.
  (previous-profile-number): Rename to 'previous-generation-number'.
  (profile-number): Rename to 'generation-number'.
  (roll-back): Rename 'previous-profile' to 'previous-generation'.

gnu: Add python2-sqlite.

* gnu/packages/python.scm (python2-sqlite): New variable.

Thank Matthias and Yutaka.

daemon: Use 'int' instead of the internal 'gcry_md_algo_t' type.

Fixes compilation with the forthcoming libgcrypt 1.6.x.
Reported by Matthias Wachs <wachs@net.in.tum.de>
and NIIBE Yutaka <gniibe@fsij.org>.

* nix/libutil/gcrypt-hash.cc (guix_hash_init, guix_hash_final): Use
  'int' as the type of the 'algo' parameter.
* nix/libutil/gcrypt-hash.hh: Update declarations accordingly.

gnu: avahi, dbus: Use /var as $localstatedir.

* gnu/packages/avahi.scm (avahi): Pass '--localstatedir'; add
  'patch/localstatedir'.
* gnu/packages/glib.scm (dbus): Pass '--localstatedir' and
  '--with-session-socket-dir'; add 'patch/localstatedir'.
* gnu/packages/patches/avahi-localstatedir.patch,
  gnu/packages/patches/dbus-localstatedir.patch: New files.
* gnu-system.am (dist_patch_DATA): Add them.

gnu: Update python-babel, python2-babel to 1.3.

* gnu/packages/python.scm (python-babel, python2-babel): Update to 1.3.