system: Add btrfs file system support.

* gnu/build/file-systems.scm (%btrfs-endianness, btrfs-superblock?,
  read-btrfs-superblock, btrfs-superblock-uuid,
  btrfs-superblock-volume-name, check-btrfs-file-system): New variables.
  (%paritition-label-readers, %partition-uuid-readers): Add btrfs
  readers.
* gnu/system/linux-initrd.scm (linux-modules): Add btrfs modules when a
  btrfs file-system is used.
* gnu/tests/install.scm (%btrfs-root-os %btrfs-root-os-source,
  %btrfs-root-installation-script, %test-btrfs-root-os): New system
  test.
* doc/guix.texi: Adjust accordingly.

Fixes <http://bugs.gnu.org/19280>.

file-systems: Refactor file-system predicates.

* gnu/build/file-systems.scm (partition-field-reader,
  read-partition-field, %partition-label-readers,
  %partition-uuid-readers, read-partition-label, read-partition-uuid):
  New variables.
  (partition-predicate, partition-label-predicate,
  partition-uuid-predicate, luks-partition-uuid-predicate): Use
  partition field readers.
  (find-partition): New variable.
  (find-partition-by-label, find-partition-by-uuid,
  find-partition-by-luks-uuid): Use find-partition-by.

file-systems: Refactor check-file-system.

* gnu/build/file-systems.scm (check-file-system): Use file-system type
  specific checker.
  (check-ext2-file-system): New variable.

file-systems: Refactor file system detection logic.

* gnu/build/file-systems.scm (read-superblock,
  null-terminated-latin1->string): New variables.
  (sub-bytevector): Move to general section.
  (ext2-superblock?, read-ext2-superblock): New variables.
  (ext2-superblock-uuid, ext2-superblock-volume-name): Use
  sub-bytevector and null-terminated-latin1->string.
  (%ext2-sblock-magic, %ext2-sblock-creator-os, %ext2-sblock-uuid,
  %ext2-sblock-volume-name): Inline constants.
  (luks-superblock?, read-luks-header): New variables.
  (%luks-header-size, %luks-magic): Inline.
  (partition-label-predicate, partition-uuid-predicate,
  luks-partition-uuid-predicate): Use new functions.

Merge remote-tracking branch 'origin/master' into staging

gnu: cross-base: Move phases to (gnu build cross-toolchain).

* gnu/packages/cross-base.scm (cross-gcc-arguments) <#:phases>: Use
'cross-gcc-build-phases', and move body cross-toolchain.scm.
(cross-gcc): Add #:imported-modules.  Add (gnu build cross-toolchain) to
 #:modules.
* gnu/build/cross-toolchain.scm: New file, with code from
'cross-gcc-arguments'.
* gnu/local.mk (GNU_SYSTEM_MODULES): Add it.

Merge branch 'master' into staging

Merge branch 'master' into python-build-system

gnu: Allow nfs file systems to be automatically mounted.

* gnu/build/file-systems.scm (mount-file-system): Append target addr= when
mounting nfs filesystems.

vm: Avoid needless file copy in 'load-in-linux-vm'.

Reported by Chris Webber.

* gnu/build/vm.scm (load-in-linux-vm)[image-file]: Remove.  Directly
refer to OUTPUT instead.

Merge branch 'master' into python-build-system

Merge branch 'master' into staging

install: Enable "cryptodisk" handling in GRUB.

This allows 'grub-install' to do the right thing when / or /boot is a
LUKS-encrypted partition.

Fixes <http://bugs.gnu.org/21843>.

* gnu/build/install.scm (install-grub): Add 'setenv' to set
'GRUB_ENABLE_CRYPTODISK'.
(wait-for-screen-text): New test.
* gnu/tests/base.scm (run-basic-test): Add #:initialization parameter
and honor it.
* gnu/tests/install.scm (%encrypted-root-os)[kernel-arguments]: Remove.
(%encrypted-root-installation-script): Pass '--uuid' to 'cryptsetup
luksFormat'.  Remove 'sed' invocation.
(enter-luks-passphrase): New procedure.
(%test-encrypted-os)[value]: Pass #:initialization to 'run-basic-test'.

marionette: Add 'marionette-screen-text' using OCR.

* gnu/build/marionette.scm (marionette-screen-text): New procedure.
* gnu/tests/base.scm (run-basic-test)["screen text"]: New test.

marionette: Delay synchronization with the host's REPL.

* gnu/build/marionette.scm (<marionette>)[marionette-repl]: Rename to...
[%marionette-repl]: ... this.
(marionette-repl): New macro.
(make-marionette): Wrap last 'read' call into 'delay', making the last
argument to 'marionette' a promise of a port.
(marionette-eval): Use 'force' in 'match' clause.

marionette: Avoid use of SIGALRM for timeouts.

* gnu/build/marionette.scm (make-marionette)[accept*]: New procedures.
Remove calls to 'sigaction'.  Use 'accept*' instead of 'accept'.

container: Pass a list of <file-system> objects as things to mount.

* gnu/build/linux-container.scm (mount-file-systems): 'mounts' is now a
list of <file-system> objects instead of a list of lists ("specs").
Add call to 'file-system->spec' as the argument to 'mount-file-system'.
(run-container, call-with-container): Adjust docstring accordingly.
* gnu/system/file-systems.scm (spec->file-system): New procedure.
* gnu/system/linux-container.scm (container-script)[script]: Call
'spec->file-system' inside gexp.
* guix/scripts/environment.scm (launch-environment/container): Remove
call to 'file-system->spec'.
* tests/containers.scm ("call-with-container, mnt namespace")
("call-with-container, mnt namespace, wrong bind mount"): Pass a list of
<file-system> objects.

Merge branch 'master' into core-updates

install: Extract procedure: install-grub-config.

* gnu/build/install.scm (install-grub-config): New procedure.
(install-grub): Use it.

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

gnu: build: file-system: Change url of LUKS specification.

* gnu/build/file-system.scm: Change url of LUKS specification.

Signed-off-by: Efraim Flashner <efraim@flashner.co.il>