doc: Mention Kiselyov's work on "staging".

* doc/guix.texi (G-Expressions): Mention Oleg's work on "staging" in
  footnote.

doc: Minor improvements in "G-Expressions".

* doc/guix.texi (G-Expressions): Show coreutils version number in store
  file name.  Add xref to "Derivations", in documentation of
  'gexp->derivation'.  Fix typo.

system: Add first-class file system declarations.

* gnu/system.scm (<operating-system>)[initrd]: Default to
  'qemu-initrd'.
  (<file-system>): New record type.
  (operating-system-root-file-system): New procedure.
  (operating-system-derivation): Take the device name for GRUB from
  'operating-system-root-file-system'.  Pass the
  'operating-system-initrd' procedure the list of boot file systems.
* gnu/system/linux-initrd.scm (file-system->spec): New procedure.
  (qemu-initrd): Add 'file-systems' parameter, and remove #:mounts
  parameter.
  [file-system-type-predicate]: New procedure.
  [linux-modules]: Use it.
  Adjust #:mounts argument in 'boot-system' call.
  (gnu-system-initrd): Remove.
* gnu/system/vm.scm (%linux-vm-file-systems): New variable.
  (expression->derivation-in-linux-vm): Adjust call to 'qemu-initrd'.
  (virtualized-operating-system): New procedure.
  (system-qemu-image/shared-store-script)[initrd]: Remove.  Use
  'virtualized-operating-system'.  Get the 'initrd' file from OS-DRV.
* guix/build/linux-initrd.scm (mount-qemu-smb-share, mount-qemu-9p):
  Remove.
  (MS_RDONLY, MS_BIND): New global variables.
  (bind-mount): Remove local 'MS_BIND' definition.
  (mount-root-file-system): New procedure, with code formerly in
  'boot-system'.
  (mount-file-system): New procedure.
  (boot-system): Add #:root-fs-type parameter.  Remove 'MS_RDONLY' local
  variable.  Use 'mount-root-file-system' and 'mount-file-system'.
* doc/guix.texi (Using the Configuration System): Add 'file-system'
  declaration.

monads: Hide 'derivation-expression' and 'lower-inputs'.

* guix/monads.scm: Unexport 'lower-inputs' and 'derivation-expression'.
  (text-file*): Add comment about the switch to 'gexp->derivation'.
  (lower-inputs): Add comment about its doom.
  (derivation-expression): Likewise.
* guix/gexp.scm (lower-inputs*): Rename to...
  (lower-inputs): ... this.  Update callers.
* tests/monads.scm (derivation-expression): New procedure.
* doc/guix.texi (The Store Monad): Use 'gexp->derivation' instead of
  'derivation-expression'.  Remove documentation of
  'derivation-expression'.
* guix/ui.scm (read/eval): Use THE-ROOT-MODULE so that macros are
  properly expanded.
* tests/guix-build.sh: Use 'gexp->derivation' instead of
  'derivation-expression'.monads: Hide 'derivation-expression' and 'lower-inputs'.

services: Rewrite using gexps.

* gnu/services.scm (<service>)[inputs]: Remove.
* gnu/system.scm (links): Remove.
  (etc-directory): Add PASSWD and SHADOW to #:inputs.
  (operating-system-boot-script): Pass ETC to 'dmd-configuration-file'.
  (operating-system-derivation): Remove EXTRAS from the union.
* gnu/system/linux.scm (pam-service->configuration): Rewrite in terms of
  'gexp->derivation'.  Compute the contents on the build side.  Expect
  'arguments' to contain a list of gexps.
  (pam-services->directory): Rewrite in terms of 'gexp->derivation'.
  (unix-pam-service): Change 'arguments' to a list of one gexp.
* gnu/system/shadow.scm (<user-account>)[inputs]: Remove.
  [shell]: Change default value to a gexp.
  (passwd-file): Rewrite in terms of 'gexp->derivation'.  Compute
  contents on the build side.
* gnu/services/base.scm (host-name-service, mingetty-service,
  nscd-service, syslog-service, guix-service): Change 'start' and 'stop'
  to gexps; remove 'inputs' field.
  (guix-build-accounts): Change 'shell' field to a gexp.
* gnu/services/networking.scm (static-networking-service): Change
  'start' and 'stop' to gexps; remove 'inputs' field.
* gnu/services/xorg.scm (slim-service): Likewise.
* gnu/services/dmd.scm (dmd-configuration-file): Expect ETC to be a
  derivation.  Change 'config' to a gexp.  Use 'gexp->file' instead of
  'text-file'.
* doc/guix.texi (Defining Services): Update nscd example with gexps, and
  without 'inputs'.  Add xref to "G-Expressions".

Add (guix gexp).

* guix/gexp.scm: New file.
* tests/gexp.scm: New file.
* Makefile.am (MODULES): Add guix/gexp.scm.
  (SCM_TESTS): Add tests/gexp.scm.
* doc/guix.texi (Derivations): Add #:inputs in 'derivation' example.
  Mark 'build-expression->derivation' as deprecated, refer to
  "G-Expressions".  Remove paragraph about code strata.
  (G-Expressions): New node.

doc: Expect to fix typo.

* doc/guix.texi (Build Systems): "except" it is.

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

guix system: Add 'vm-image' action and '--image-size' option.

* guix/scripts/system.scm (%options): Add --image-size.
  (%default-options): Add 'image-size'.
  (guix-system)[parse-options]: Handle the 'vm-image' action.
  Honor them.
  (show-help): Update accordingly.
* doc/guix.texi (Invoking guix system): Add 'vm-image'.

doc: Add "Build Systems" section.

* doc/guix.texi (Defining Packages): Add 'arguments' field in the
  example; update 'synopsis' and 'description'.  Remove most of the
  description of 'build-system', and instead reference to the "Build
  Systems" node.  Briefly describe 'arguments' field, and remove more
  elaborate description.  Add cross-reference to "Packaging Guidelines".
  (Build Systems): New node.
  (Packaging Guidelines): Mention '--log-file'.

doc: Update description of the chroot contents.

* doc/guix.texi (Build Environment Setup): Adjust description of /dev
  and /proc; remove footnote about /dev/shm, now obsolete.

doc: fix typo.

* doc/guix.texi (Substitutes): add a missing 's'.

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

doc: Document substitutes.

* doc/guix.texi (Invoking guix-daemon): Add cross-reference to
  "Substitutes".
  (Features): Remove footnote about unauthenticated substitutes.  Link
  to "Substitutes".
  (Substitutes): New node.
  (Invoking guix build): Link to "Substitutes".
  (Packaging Guidelines): Likewise.

Merge branch 'master' into core-updates

offload: Allow build machines to specify a port number.

* guix/scripts/offload.scm (<build-machine>): Add 'port' field.
  (remote-pipe, send-files): Use lsh's '-p' option when invoking it.

guix build: Add '--with-source'.

* guix/scripts/build.scm (package-with-source): New procedure.
  (show-help): Add '--with-source'.
  (%options): Likewise.
  (options->derivations): Call 'options/with-source' and
  'options/resolve-packages'.
  (options/resolve-packages, options/with-source): New procedures.
* doc/guix.texi (Invoking guix build): Document '--with-source'.

Merge branch 'master' into core-updates

doc: Update packaging guidelines.

* HACKING (Submitting Patches): Mention 'git send-mail'.
* doc/guix.texi (Packaging Guidelines): More details on how to prepare a
  package module.
  (Contributing): Add reference to #guix channel on Freenode.

Co-authored-by: Ludovic Courtès <ludo@gnu.org>

guix build: Add '--timeout' to the common build options.

* guix/scripts/build.scm (show-build-options-help): Document
  '--timeout'.
  (set-build-options-from-command-line): Pass #:timeout to
  'set-build-options'.
  (%standard-build-options): Add '--timeout'.
* doc/guix.texi (Invoking guix build): Document it.

Change the default store file name to /gnu/store.

* configure.ac: Change the default 'storedir' to /gnu/store.  Print
  $storedir.
* doc/guix.texi: Replace "/nix/store" by "/gnu/store", except where
  describing Nix compatibility.
* Makefile.am: Likewise.

doc: Explain what's special about the (gnu packages ...) name space.

* doc/guix.texi (Invoking guix package): Explain where packages are
  searched for and link to "Package Modules".
  (Defining Packages) <example>: Use 'define-module' clause instead of
  'use-modules'.  Explain why and link to "Package Modules".
  (Invoking guix build): Explain where packages aer searched for and
  link to "Package Modules".
  (Package Modules): Explain that (gnu packages ...) is scanned.