services: Add 'udisks-service'.

* gnu/services/desktop.scm (<udisks-configuration>): New record type.
  (udisks-service-type): New variable.
  (udisks-service): New procedure.
  (%desktop-services): Use it.
* doc/guix.texi (Desktop Services): Document it.

services: 'polkit-service-type' can now be extended.

* gnu/packages/polkit.scm (polkit)[source]: Adjust snippet so that rules
  and actions are looked for under /etc/polkit-1.
* gnu/services/desktop.scm (<polkit-configuration>): New record type.
  (polkit-directory, polkit-etc-files, polkit-setuid-programs): New
  procedures.
  (polkit-service-type)[compose, extend]: New fields.
  (polkit-service): Refine docstring.
  (colord-service-type): Extend POLKIT-SERVICE-TYPE.
  (elogind-configuration-file): Extend POLKIT-SERVICE-TYPE.
* doc/guix.texi (Desktop Services): Update 'polkit-service'
  documentation.

doc: Suggest diffing things with --no-dereference.

* doc/guix.texi (Invoking guix challenge): Add --no-dereference in
  'diff' example.

emacs: Add key bindings for 'guix-build-log-minor-mode'.

* emacs/guix-build-log.el (guix-build-log-mode-map): Move keys to ...
  (guix-build-log-common-map): ...here.  New variable.
  (guix-build-log-minor-mode-map): New variable.
  (guix-build-log-minor-mode): Use it.
* doc/emacs.texi (Emacs Build Log): Document it.

services: 'tor-service' takes a 'config-file' parameter.

* gnu/services/networking.scm (tor-dmd-service): Take a 'config'
  parameter and honor it.
  (tor-service): Take a 'config-file' parameter.  Pass it in the
  service's value.
* doc/guix.texi (Networking Services): Adjust accordingly.

scripts: environment: Allow lists of packages in expressions.

* guix/scripts/environment.scm (options/resolve-packages): Match against
  lists of packages when evaluating expressions.
* tests/guix-environment.sh: Add test.
* doc/guix.texi ("invoking guix environment"): Add docs.

system: Add 'locale-libcs' field.

* gnu/system/locale.scm (localedef-command)[maybe-version-directory]:
  New procedure.
  Use it.
  (locale-directory): Rename to...
  (single-locale-directory): ... this.  Check the version of LIBC to
  determine whether to create a "X.Y" sub-directory or to make it a
  symlink to ".".  Add the version number in the derivation name.
  (locale-directory): New procedure.
  (%default-locale-libcs): New variable.
* gnu/system.scm (<operating-system>)[locale-libcs]: New field.
  (operating-system-locale-directory): Pass it to 'locale-directory'.
* doc/guix.texi (operating-system Reference): Document 'locale-libcs'.
  (Locales)[Locale Data Compatibility Considerations]: New section.

scripts: system: Add 'container' action.

* guix/scripts/system.scm (show-help): Display 'container' action.
  (system-derivation-for-action, guix-system): Add 'container' case.
  (perform-action): Skip GRUB config generation when building a container.
* doc/guix.texi (Invoking guix system): Document it.

Merge branch 'master' into dbus-update

doc: Fix outdated description of the bare-bones example.

Reported by fps on #guix.

* doc/guix.texi (Using the Configuration System): Replace mention of
  Emacs with tcpdump.

scripts: environment: Allow mixing regular and ad-hoc packages.

This patch changes the --ad-hoc flag to be positional.  That is, the
packages that appear before --ad-hoc are interpreted as packages whose
inputs should be in the environment; the packages that appear after are
interpreted as packages to be directly added to the environment.

* guix/scripts/environment.scm (tag-package-arg, compact): New
  procedures.
  (%options): Tweak the handlers for --load and --expression options.
  (options/resolve-packages): Preserve package mode tag.
  (parse-args): Tweak argument handler to use package tagging procedure.
  (guix-environment): Apply ad-hoc behavior on a per package basis.
* tests/guix-environment.sh: Add test.
* doc/guix.texi ("invoking guix environment"): Document new behavior of
  --ad-hoc.

services: Add screen-locker service.

* gnu/system/linux.scm (base-pam-services): Remove "xlock" and
  "xscreensaver".
* gnu/services/xorg.scm (<screen-locker>): New record type.
  (screen-locker-pam-services, screen-locker-setuid-programs,
  screen-locker-service): New procedures.
  (screen-locker-service-type): New variable.
* gnu/services/desktop.scm (%desktop-services): Use them.
* doc/guix.texi (X Window): Document 'screen-locker-service'.
  (Desktop Services): Mention it.

doc: Mention Nix in the intro.

* doc/guix.texi (Introduction): Mention Nix with a xref to
  "Acknowledgments".
  (Acknowledgments): Add link to nixos.org.

services: Add 'modify-services'.

* gnu/services.scm (%modify-service, modify-services): New macros.
* gnu/services/base.scm (mingetty-service-type, guix-service-type):
  Export.
* emacs/guix-devel.el (guix-devel-keywords): Add 'modify-services'.
  Ditto in 'guix-devel-scheme-indent' call.
* doc/guix.texi (Using the Configuration System): Give an example of
  'modify-services'.
  (Service Reference): Document it.

services: 'guix-configuration' has a 'substitute-urls' field.

* gnu/services/base.scm (<guix-configuration>)[substitute-urls]: New
  field.
  (guix-dmd-service): Honor it.
* doc/guix.texi (Base Services): Document it.

refresh: Support comma-separated updater types.

* guix/scripts/refresh.scm (%options): Handle comma-separated types for
  '--type' option.
  (guix-refresh): Adjust accordingly.
  (show-help): Likewise.
* doc/guix.texi (Invoking guix refresh): Document it.

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.

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.

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.

guix system: Add the 'list-generations' command.

* guix/scripts/system.scm (display-system-generation, list-generations):
  New procedures.
  (process-action): Clarify docstring.
  (process-command): New procedure.
  (guix-system)[parse-sub-command]: Add 'list-generations'
  Call 'process-command' instead of 'process-action'.
* doc/guix.texi (Using the Configuration System): Mention generations,
  rollback, and 'list-generations'.
  (Invoking guix system): Document 'list-generations'.