store: Use the daemon's substitute URLs by default.

Partly fixes <http://bugs.gnu.org/20217>.

* guix/store.scm (set-build-options): Change #:substitute-urls to
  default to #f.  Send the 'substitute-urls' pair only if
  SUBSTITUTE-URLS is true.
* guix/scripts/build.scm (set-build-options-from-command-line): Do not
  default to %DEFAULT-SUBSTITUTE-URLS for #:substitute-urls.
* guix/scripts/size.scm (%default-options): Remove 'substitute-urls'.

scripts: build: Add --file option.

* guix/scripts/build.scm (show-help): Add help text for --file option.
  (%options): Add --file option.
  (options/resolve-packages): Handle 'file' options.
* tests/guix-build.sh: Add tests.
* doc/guix.texi ("invoking guix build"): Add doc.

gnu: python-debian: Avoid @itemize in description.

* gnu/packages/python.scm (python-debian): Use @enumerate instead of
  @itemize.

substitute: Honor all the specified server URLs.

* guix/scripts/substitute.scm (lookup-narinfos/diverse): New procedure.
  (lookup-narinfo): Use it.
  (process-query): Change #:cache-url to #:cache-urls.
  [valid?]: Remove 'narinfo?' check, which is no longer necessary.
  Use 'lookup-narinfos/diverse' instead of 'lookup-narinfos'.
  (process-substitution): Change #:cache-url to #:cache-urls.
  (%cache-url): Rename to...
  (%cache-urls): ... this.  Turn into a list.
  (guix-substitute): Remove 'getaddrinfo' test with early exit.  Adjust
  calls to 'process-query' and 'process-substitution'.
* tests/substitute.scm: Change '%cache-url' to '%cache-urls'.

substitute: 'lookup-narinfos' returns exactly a list of narinfos.

* guix/scripts/substitute.scm (lookup-narinfos): Filter out #f values
  from CACHED, such that the end result is exactly a list of narinfos,
  not interspersed with #f.
* guix/scripts/challenge.scm (discrepancies): Assume REMOTE is a list of
  narinfos.

substitute: 'http-multiple-get' follows 'fold' style.

* guix/scripts/substitute.scm (http-multiple-get): Add 'seed'
  parameter.  Call PROC in 'fold' style.
  (fetch-narinfos)[handle-narinfo-response]: Adjust accordingly.
  Update 'http-multiple-get' call accordingly.

gnu: grub: Install documentation.

* gnu/packages/grub.scm (grub)[native-inputs]: Add help2man and texinfo.

gnu: grub: Use modify-phases and other minor cleanups.

* gnu/packages/grub.scm (grub)[arguments]: Use modify-phases.  Return #t from
  'patch-stuff' phase.  Add 'patch-stuff' phase after 'unpack' instead of
  before 'patch-source-shebangs'.
  [inputs]: Add comment noting that 'fuse' would be a desirable input.

doc: Add texinfo to the requirements when building from git.

* doc/contributing.texi (Building from Git): Add GNU Texinfo to the list of
  additional requirements.

gnu: linux-libre: On MIPS, the linux image name is vmlinuz, not bzImage.

* gnu/packages/linux.scm (linux-libre)[install-phase]: Add vmlinuz to the list
  of file names to be copied.

gnu: linux-libre: Add case for ARCH=mips.

* gnu/packages/linux.scm (linux-libre)[build-phase]: When setting ARCH, add a
  case for MIPS.

gnu: linux-libre: Add 'supported-systems' field: Intel only for now.

* gnu/packages/linux.scm (linux-libre)[supported-systems]: New field.

gnu: linux-libre: Update to 4.2.5.

* gnu/packages/linux.scm (linux-libre): Update to 4.2.5.

linux-initrd: Use pata_acpi, pata_atiixp, and isci modules only on Intel.

* gnu/system/linux-initrd.scm (base-initrd)[linux-modules]: Include
  "pata_acpi", "pata_atiixp", and "isci" on Intel systems only.

system: grub: Adjust eye-candy to work on non-Intel systems.

* gnu/system/grub.scm (eye-candy): Accept additional 'system' argument.  Add
  local 'setup-gfxterm-body' variable.  Replace the 'load_video' grub function
  with 'setup_gfxterm', which includes everything in the 'if loadfont' form on
  Intel systems, but is empty on non-Intel.
  (grub-configuration-file): Pass 'system' to 'eye-candy.

system: grub: On MIPS, the linux image name is vmlinuz, not bzImage.

* gnu/system/grub.scm (grub-configuration-file): Add 'linux-image-name'
  internal procedure.  Use it from 'entry->gexp'.

gnu: Add Diffoscope.

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

gnu: Add python-chardet.

* gnu/packages/python.scm (python-chardet, python2-chardet): New
  variables.

gnu: Add python-debian.

* gnu/packages/python.scm (python-debian, python2-debian): New
  variables.

refresh: Add '--list-updaters' option.

* guix/scripts/refresh.scm (list-updaters-and-exit): New procedure.
  (%options, show-help): Add '--list-updaters' option.
* doc/guix.texi (Invoking guix refresh): Document it.