edit: Improve error reporting when $EDITOR is not found.

Reported by Benno Evers <benno@bmevers.de>
at <https://lists.gnu.org/archive/html/guix-devel/2015-11/msg00125.html>.

* guix/scripts/edit.scm (guix-edit): Wrap 'execl' call in 'catch'.
  Provide more meaningful error message.

edit: Lift helper procedure.

* guix/scripts/edit.scm (package->location-specification): New
  procedure, with code formerly...
  (guix-edit): ... here.  Use it.

import: hackage: Fix invalid use of 'leave'.

Reported by Paul van der Walt <paul@denknerd.org>
in <http://bugs.gnu.org/21829>.

* guix/scripts/import/hackage.scm (guix-import-hackage): Add missing
  argument in call to 'leave'.

build-system/python: 'package-with-python2' preserves source location.

* guix/build-system/python.scm (package-with-explicit-python): Add
  'location' field.

import: pypi: Make downloads silent.

* guix/import/pypi.scm (pypi-fetch): Wrap body in
  'call-with-output-file' and 'with-error-to-port'.

import: pypi: Add missing copyright line.

* guix/import/pypi.scm: Add missing copyright line for bab020d.

scripts: container: Fix 'exec' command line parsing.

* guix/scripts/container/exec.scm (partition-args): Reimplement such
  that all args up to and including the PID are returned as the first of
  the two values.

import: pypi: add updater

* guix/import/pypi.scm (guix-package->pypi-name,
  latest-release): New procedures.
  (%pypi-updater): New variable.
* guix/scripts/refresh.scm (%updaters): Add %PYPI-UPDATER.
* doc/guix.texi (Invoking guix refresh): Mention PyPI

import: pypi: Use "pypi-uri" instead of building the URL manually.

* guix/import/pypi.scm (make-pypi-sexp): Use "pypi-uri".
* tests/pypi.scm: Update the tests accordingly.

guix: Add a "pypi-uri" helper method.

* guix/download.scm (mirrors): New "pypi" mirror.
* guix/build-system/python.scm (pypi-uri): New method.

scripts: environment: Display friendly container error messages.

* guix/scripts/environment.scm (assert-container-features): New
  procedure.
  (guix-environment): Use it.

import: gnu: Update to the (guix upstream) API.

This is a followup to 0a7c5a0.

* guix/import/gnu.scm (preferred-archive-type): Use
  'upstream-source-archive-types' instead of 'gnu-release-archive-types'.
  (gnu-package->sexp): Use 'upstream-source-urls' et al.  Update call to
  'download-tarball'.
  (gnu->guix-package): Use <upstream-source> instead of <gnu-release>.
* guix/upstream.scm (upstream-source-archive-types): Export.

guix system: Always build grub.cfg for 'init' and 'reconfigure'.

Fixes <http://bugs.gnu.org/21068>.
Reported by Germano Gabbianelli <tyrion.mx@gmail.com>
and Mark H Weaver <mhw@netris.org>.

* guix/scripts/system.scm (perform-action): Always add GRUB.CFG to DRVS
  for 'init' and 'reconfigure'.

Co-authored-by: Mark H Weaver <mhw@netris.org>

services: Add 'system-service-type'.

* gnu/services.scm (system-derivation): New procedure.
  (system-service-type): New variable.
  (boot-script-entry): New procedure.
  (boot-service-type): Extend SYSTEM-SERVICE-TYPE.
  (etc-entry): New procedure.
  (etc-service-type): Extend SYSTEM-SERVICE-TYPE.
  (fold-services): Change default #:target-type to SYSTEM-SERVICE-TYPE.
* gnu/system.scm (operating-system-directory-base-entries): New procedure.
  (essential-services): Use it.  Add an instance of
  SYSTEM-SERVICE-TYPE.
  (operating-system-boot-script): Pass #:target-type to 'fold-services'.
  (operating-system-derivation): Rewrite in terms of 'fold-services'.
* gnu/system/linux-container.scm (system-container): Remove.
  (container-script): Use 'operating-system-derivation'.
* guix/scripts/system.scm (export-extension-graph): Replace
  BOOT-SERVICE-TYPE by SYSTEM-SERVICE-TYPE.
* doc/images/service-graph.dot: Add 'system' node and edges.
* doc/guix.texi (Service Composition): Mention SYSTEM-SERVICE-TYPE.
  (Service Reference): Document it.  Update 'fold-services'
  documentation.

scripts: environment: Ignore user shell when spawning container.

* guix/scripts/environment.scm (%default-options): Remove 'exec'
  association.
  (guix-environment): If the user didn't specify a command, use the
  default shell, or use /bin/sh when a container is requested.

emacs: Add completions for '--type' option of 'refresh' popup.

* guix/scripts/refresh.scm: Export '%updaters'.
* emacs/guix-main.scm (refresh-updater-names): New procedure.
* emacs/guix-base.el (guix-refresh-updater-names): New function.
* emacs/guix-read.el (guix-read-refresh-updater-names,
  guix-read-refresh-updater-names-string): New functions.
* emacs/guix-command.el (guix-command-improve-refresh-argument): Use
  'guix-read-refresh-updater-names-string'.

scripts: Add 'container' subcommand.

* guix/scripts/container.scm: New file.
* guix/scripts/container/exec.scm: New file.
* po/guix/POTFILES.in: Add them.
* Makefile.am (MODULES): Add them.
* doc/guix.texi (Invoking guix container): New section.

guix system: Fix typo in --help message.

* guix/scripts/system.scm (show-help): Align 'container' the same way as
  other actions.

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.

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.