offload: Move macro definitions before use.

* guix/scripts/offload.scm (lock-file, unlock-file, with-file-lock,
  with-machine-lock, machine-slot-file, acquire-build-slot,
  release-build-slot): Move definitions above their first use.

offload: Distinguish between 'decline' and 'postpone'.

* guix/scripts/offload.scm (transfer-and-offload): New procedure, with
  core formerly in 'process-request'.
  (choose-build-machine): Remove 'requirements' parameter.
  (process-request): Reply 'decline' when none of MACHINES matches the
  requirements, and 'postpone' when MACHINES are busy.

offload: Prevent locked files from being GC'd.

* guix/scripts/offload.scm (%slots): New variable.
  (choose-build-machine): Add SLOT to '%slots'.

offload: Fix thinko.

* guix/scripts/offload.scm (choose-build-machine)[machine+slots]: Use
  'filter-map', not 'filter'.

offload: Make 'parallel-builds' a hard limit.

* guix/scripts/offload.scm (machine-choice-lock-file,
  machine-slot-file, acquire-build-slot, release-build-slot): New
  procedures.
  (choose-build-machine): Operate with (machine-choice-lock-file)
  taken.  Acquire a build slot for each of MACHINES.  Release those not
  used.

offload: Further generalize lock files.

* guix/scripts/offload.scm (lock-machine, unlock-machine): Remove.
  (lock-file, unlock-file): New procedures.
  (with-file-lock): New macro.
  (with-machine-lock): Rewrite in terms of 'with-file-lock'.

offload: Generalize the machine lock mechanism.

* guix/scripts/offload.scm (lock-machine): Add 'hint' parameter.
  (unlock-machine): Remove 'machine' parameter.
  (with-machine-lock): Add 'hint' parameter, and pass it down.
  (process-request): Adjust uses of 'with-machine-lock' to pass the
  'bandwidth hint.

offload: Serialize file transfers to build machines.

* guix/scripts/offload.scm (machine-lock-file, lock-machine,
  unlock-machine): New procedures.
  (with-machine-lock): New macro.
  (process-request): Wrap 'send-files' and 'retrieve-files' calls in
  'with-machine-lock'.

guix package: Use the common build options from (guix scripts build).

* guix/scripts/build.scm (%standard-build-options): Change option
  handlers to support multiple seeds.
* guix/scripts/package.scm (show-help): Remove --dry-run, --fallback,
  --no-substitutes, and --max-silent-time.
  (%options): Likewise, and add %STANDARD-BUILD-OPTIONS.
  (%default-options): Add 'verbosity'.
  (guix-package): Call 'set-build-options-from-command-line' instead of
  'set-build-options'.

substitute-binary: Gracefully handle HTTP GET errors.

* guix/http-client.scm (&http-get-error): New condition type.
  (http-fetch): Raise it instead of using 'error'.
* guix/scripts/substitute-binary.scm (fetch) <http>: Wrap body into
  'guard' form; gracefully handle 'http-get-error?' conditions.

offload: Comment out attempt to set up an lsh gateway.

* guix/scripts/offload.scm (open-ssh-gateway): Comment out.
  (process-request): Remove call to 'open-ssh-gateway' and to 'kill'.

offload: 'remote-pipe' uses the right SSH key.

* guix/scripts/offload.scm (remote-pipe): Pass -i when invoking
  %LSHG-COMMAND.

offload: Take the target machine load into account.

* guix/scripts/offload.scm (machine-load, machine-less-loaded?,
  machine-less-loaded-or-faster?): New procedures.
  (choose-build-machine): Use 'machine-less-loaded-or-faster?' when
  sorting.  Return the head of MACHINES unless it's loaded is >= 2.

guix archive: Change '--help' to show '--authorize'.

* guix/scripts/archive.scm (show-help): Add '--authorize'.

guix hash: Add '--recursive'.

* guix/scripts/hash.scm (show-help): Add --recursive.
  (%options): Likewise.
  (guix-hash)[file-hash]: New procedure.  Honor --recursive.
  Use it.
* guix/nar.scm (write-file): Add missing field to the &nar-error
  condition raised upon unsupported file type; change its message to be
  more descriptive.
* tests/guix-hash.sh: Add tests with -r.
* doc/guix.texi (Invoking guix hash): Document --recursive.

guix hash: Don't load the whole file in memory.

* guix/scripts/hash.scm (guix-hash)[eof->null]: Remove.
  (guix-hash): Use 'port-sha256' to compute the hash instead of
  'get-bytevector-all' and co.

gnu: Introduce the (gnu services ...) modules.

* gnu/system/dmd.scm: Remove file.  Move contents to...
* gnu/services.scm, gnu/services/base.scm, gnu/services/dmd.scm,
  gnu/services/networking.scm, gnu/services/xorg.scm: ... here.  New
  files.
* gnu/system.scm, gnu/system/vm.scm: Adjust accordingly.
* guix/scripts/system.scm (%user-module): Likewise.
* doc/guix.texi (Using the Configuration System): Likewise.
  (Defining Services): Likewise.

Add 'guix system'.

* guix/scripts/system.scm: New file.
* Makefile.am (MODULES): Add it.
* po/POTFILES.in: Likewise.
* doc/guix.texi (Using the Configuration System): Link to "Invoking guix
  system".
  (Invoking guix system): New node.

guix build: Factorize common options.

* guix/scripts/build.scm (show-build-options-help,
  set-build-options-from-command-line): New procedures.
  (show-help): Remove description of --dry-run,
  --fallback, --no-substitutes, --max-silent-time, and --cores.  Call
  'show-build-options-help'.
  (%standard-build-options): New variable.
  (%options): Remove --dry-run, --fallback, --no-substitutes,
  --verbosity, --max-silent-time, and --cores.  Add
  %STANDARD-BUILD-OPTIONS.
  (guix-build): Use 'set-build-options-from-command-line' instead of
  'set-build-options'.
* guix/scripts/archive.scm (show-help): Remove description of --dry-run,
  --fallback, --no-substitutes, --max-silent-time, and --cores.  Call
  'show-build-options-help'.
  (%options): Remove --dry-run, --fallback, --no-substitutes,
  --verbosity, --max-silent-time, and --cores.  Add
  %STANDARD-BUILD-OPTIONS.
  (export-from-store): Call 'set-build-options-from-command-line'
  instead of 'set-build-options.

guix build: Move 'set-build-options' call earlier.

* guix/scripts/build.scm (guix-build): Move 'set-build-options' call
  before 'show-what-to-build'.