refresh: Add end-of-line to error message.

* guix/scripts/refresh.scm (%options)[select]: Add end-of-line to
  error message.

guix lint: add the --checkers option.

* guix/scripts/lint.scm: add the "--checkers" option.
* doc/guix.texi (Invoking guix lint): Document it.
* tests/guix-lint.sh: New file
* Makefile.am (SCM_TESTS): Add it.

guix package: Add '--switch-generation' option.

* guix/scripts/package.scm (switch-to-generation): New procedure.
  (switch-to-previous-generation): Use it.
  (guix-package): Adjust for '--switch-generation' option.
* tests/guix-package.sh: Test it.
* doc/guix.texi (Invoking guix package): Document it.

profiles: Add condition types for profiles and generations.

Suggested by Ludovic Courtès.

* guix/profiles.scm (&profile-error, &profile-not-found-error,
  &missing-generation-error): New condition types.
* guix/ui.scm (call-with-error-handling): Handle new types.
* guix/scripts/package.scm (roll-back, guix-package): Raise
  '&profile-not-found-error' where needed.

scripts: Add 'environment' command.

* guix/scripts/environment.scm: New file.
* Makefile.am (MODULES): Add it.
* doc/guix.texi ("Invoking guix environment"): New node.

ui: Move 'show-manifest-transaction' from (guix profiles).

* guix/profiles.scm: Do not use (guix ui) module.
  (right-arrow, manifest-show-transaction): Move and rename to...
* guix/ui.scm (right-arrow, show-manifest-transaction): ... here.
* tests/profiles.scm ("manifest-show-transaction"): Move to...
* tests/ui.scm ("show-manifest-transaction"): ... here.
  (guile-1.8.8, guile-2.0.9): New variables.
* emacs/guix-main.scm (process-package-actions): Rename
  'manifest-show-transaction' to 'show-manifest-transaction'.
* guix/scripts/package.scm (guix-package): Likewise.

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

Break module cycle involving (guix store) and (guix ui).

Before, there was a cycle along the lines of:

  (guix store) -> (guix nar) -> (guix ui) -> (guix store)

This caused problems, as discussed at:

  http://lists.gnu.org/archive/html/guix-devel/2014-10/msg00109.html

This patch removes cycles in the (guix ...) modules.

* guix/nar.scm (&nar-error, &nar-read-error, dump, write-contents,
  read-contents, %archive-version-1, write-file, restore-file): Move to...
* guix/serialization.scm: ... here.
* guix/store.scm: Remove dependency on (guix nar).
* guix/scripts/hash.scm, guix/scripts/offload.scm,
  guix/scripts/substitute-binary.scm, tests/nar.scm, tests/store.scm,
  tests/substitute-binary.scm: Adjust accordingly.

substitute-binary: Ignore $GUIX_BINARY_SUBSTITUTE_URL.

* guix/scripts/substitute-binary.scm (%cache-url): Ignore the
  'GUIX_BINARY_SUBSTITUTE_URL' environment variable.
* test-env.in: Invoke 'guix-daemon' with '--substitute-urls'.
* tests/substitute-binary.scm: Set '%cache-url' to the value of
  'GUIX_BINARY_SUBSTITUTE_URL'.

daemon: Add '--substitute-urls' option.

* nix/nix-daemon/guix-daemon.cc (GUIX_OPT_SUBSTITUTE_URLS): New macro.
  (GUIX_OPT_NO_BUILD_HOOK, GUIX_OPT_GC_KEEP_OUTPUTS,
  GUIX_OPT_GC_KEEP_DERIVATIONS): Renumber.
  (options): Add '--substitute-urls'.
  (parse_opt): Honor it.
  (main): Add 'settings.set' call for the default "substitute-urls"
  value.
* guix/scripts/substitute-binary.scm (daemon-options,
  find-daemon-option): New procedures.
  (%cache-url): Define based on the "substitute-urls" daemon option.
* doc/guix.texi (Invoking guix-daemon): Document '--substitute-urls'.
  (Substitutes): Mention it.

guix lint: make sure synopses do not start with the package name.

* guix/scripts/lint.scm (check-start-with-package-name): New method.
* tests/lint.scm ("synopsis: start with package name"): New test.

guix lint: Make sure a synopsis cannot start with a lower-case article.

* guix/scripts/lint.scm (check-start-article): use "string-ci=?" instead of
  "string=?".
* tests/lint.scm ("synopsis: starts with 'a'",
  "synopsis: starts with 'an'"): New tests.

guix lint: check whether descriptions and synopses start with an upper-case letter.

* guix/scripts/lint.scm (check-description-style,
  check-synopsis-start-upper-case): New methods.
* tests/lint.scm ("description: does not start with an upper-case letter",
  "synopsis: does not start with an upper-case letter"): New tests.

guix lint: Make sure synopses are not too long.

* guix/scripts/lint.scm (check-synopsis-length): New procedure.
* tests/lint.scm ("synopsis: too long"): New test.

guix lint: make sure check-patches retrieves patch names.

* guix/lint (check-patches): Test the output of origin-patches.

guix package: Export generation procedures.

* guix/scripts/package.scm: Export 'roll-back', 'delete-generation',
  'delete-generations'.
  (link-to-empty-profile, roll-back): Add 'store' argument.
  (delete-generations): New procedure.
  (guix-package): Adjust accordingly.
  [delete-generation]: Move to the top level.  Add 'store' and 'profile'
  arguments.
  [display-and-delete]: Move to 'delete-generation'.

pull: Add dependency on Guile-JSON.

Reported by Alex Sassmannshausen <alex.sassmannshausen@gmail.com>.

* guix/scripts/pull.scm (unpack): Add Guile-JSON to %load-path and
  %load-compiled-path.

import: Add PyPI importer.

* guix/snix.scm: Delete.
* guix/import/snix.scm: New file.
* guix/import/pypi.scm: New file.
* guix/import/utils.scm: New file.
* guix/scripts/import/nix.scm: New file.
* guix/scripts/import/pypi.scm: New file.
* tests/pypi.scm: New file.
* tests/snix.scm: Import (guix import snix) module.
* guix/scripts/import.scm (%default-options, %options): Delete.
  (%standard-import-options, importers): New variables.
  (show-help): List importers.
  (guix-import): Factor out Nix-specific logic.  Delegate to correct importer
  based upon first argument.
* configure.ac (HAVE_GUILE_JSON): New conditional.
* Makefile.am (MODULES): Add new files and remove 'guix/snix.scm'.
  (SCM_TESTS): Add 'tests/pypi.scm' if guile-json is installed.

guix build: Add -L/--load-path as a common option.

* guix/scripts/build.scm (show-build-options-help): Document -L.
  (%standard-build-options): Add -L/--load-path.
* tests/guix-package.sh: Test it.

guix package: Use 'profile-generations'.

* guix/scripts/package.scm (guix-package)[process-actions]: Use
  'profile-generations' instead of the equivalent code.

offload: Use a total order when sorting available machines.

* guix/scripts/offload.scm (machine-less-loaded?, machine-faster?):
  Remove.
  (machine-power-factor): New procedure.
  (machine-less-loaded-or-faster?): Use it.