gexp: Slightly simplify 'gexp-inputs'.

* guix/gexp.scm (gexp-inputs)[add-reference-inputs]: Remove unneeded
'if' in the non-native nested gexp case.

gexp: Native inputs of nested gexps are properly accounted for.

Previously, 'gexp-native-inputs' would not return the native inputs of
nested gexps.  For example, this:

  (gexp-native-inputs #~(foo #$#~(bar #+coreutils)))

would return '().

* guix/gexp.scm (gexp-inputs)[add-reference-inputs]: In the
non-recursive cases, check whether N? and NATIVE? are the same, and act
accordingly.
[native-input?]: Remove.
Fold over all of (gexp-references exp).
* tests/gexp.scm ("ungexp + ungexp-native, nested, special mixture"):
New test.
* tests/gexp.scm ("input list splicing + ungexp-native-splicing"): Pass
 #:native? #t to 'gexp-input'.

import cran: Handle HTTP errors.

Fixes <http://bugs.gnu.org/23479>.

* guix/import/cran.scm (fetch-description): Return #f in case of HTTP
errors.

guix import: Print list of expressions.

* guix/scripts/import.scm (guix-import): Print list of expressions.

import cran: Add "recursive" option.

* guix/scripts/import/cran.scm: (%options): Add "recursive" option.
(guix-import-cran): Handle "recursive" option.
* doc/guix.texi (Invoking guix import): Document it.

import cran: Add recursive importer.

* guix/import/cran.scm (recursive-import): New variable.
(cran->guix-package): Memoize the procedure.

import cran: Ignore default R packages.

* guix/import/cran.scm (default-r-packages): New variable.
(description->package): Drop default R packages from list of inputs.

import cran: description->package: Also return package dependencies.

* guix/import/cran.scm (description->package): Return package
  dependencies in addition to generated package expression.

import cran: Move guix-name to top-level.

* guix/import/cran.scm (guix-name): Move to top-level.

import cran: Remove more invalid characters from package names.

* guix/import/cran.scm (guix-name): Replace period and underscore with
  dash; always prepend package names with "r-".

import cran: Handle BSD licenses with LICENSE file.

* guix/import/cran.scm (string->license): Add cases for BSD licenses
with LICENSE file.

import cran: Translate MIT to the Expat license.

* guix/import/cran.scm (string->license): Translate "MIT" license to
Expat license.

import cran: Do not use "or later" licenses by default.

* guix/import/cran.scm (string->license): Use exact license versions.

profiles: Remove dependency on 'glibc-utf8-locales' for tests.

Commit 1af0860e8be81c01ad405c1226d6bc4516e62863 added a mandatory
dependency on 'glibc-utf8-locales', which entails long rebuilds for
tests.

* guix/profiles.scm (profile-derivation): Add #:locales? parameter.
Add 'set-utf8-locale' variable.  Use it when LOCALES? is true.
(link-to-empty-profile): Pass #:locales? #f.
* guix/scripts/environment.scm (inputs->profile-derivation): Pass
  #:locales?.
* guix/scripts/package.scm (build-and-use-profile): Likewise.
* tests/packages.scm ("--search-paths with pattern"): Pass #:locales? #f.
* tests/profiles.scm ("profile-derivation")
("profile-derivation, inputs", "profile-manifest, search-paths")
("etc/profile", "etc/profile when etc/ already exists"):
("etc/profile when etc/ is a symlink"): Likewise.

profiles: Build profiles in a UTF-8 locale.

Fixes <http://bugs.gnu.org/25213>.
Reported by Christopher Baines <mail@cbaines.net>.

* guix/profiles.scm (profile-derivation)[glibc-utf8-locales]: New
variable.
[builder]: Use it to set 'LOCPATH'.

download: Protect against dangling symlinks in $SSL_CERT_DIR.

Reported by Christopher Baines <mail@cbaines.net>
in <https://bugs.gnu.org/25213>.

* guix/build/download.scm (make-credendials-with-ca-trust-files): Check
whether FILE exists before calling
'set-certificate-credentials-x509-trust-file!'.

refresh: Make dependency on (guix import crates) weak.

Reported by Tobias Geerinckx-Rice <me@tobias.gr>.

* guix/scripts/refresh.scm: Do not explicitly import (guix import crates).

upstream: Determine archive type correctly.

* guix/upstream.scm (package-update): Take the basename of the uri
  before trying to determine the extension.

graph: Add d3js backend.

* d3.v3.js, graph.js: New files.
* Makefile.am (EXTRA_DIST): List them.
* guix/graph.scm (%d3js-backend): New variable.
(emit-d3js-prologue, emit-d3js-epilogue, emit-d3js-node,
emit-d3js-edge): New procedures.
(%graph-backends): Add %d3js-backend.

graph: Add "list-backend" and "backend" options.

* guix/graph.scm (%graph-backends): New variable.
* guix/scripts/graph.scm (lookup-backend, list-backends): New
procedures.
(%options): Add options for "backend" and "list-backends".
(show-help): Add help texts for "backend" and "list-backend" options.
(%default-options): Add "backend" default.
(guix-graph): Pass backend argument to "export-graph".
* doc/guix.texi (Invoking guix graph): Document the new options.