gnu-maintenance: Support .zip files.

Reported by Andreas Enge <andreas@enge.fr>.

* guix/gnu-maintenance.scm (sans-extension): Add case for ".zip".
  (%tarball-rx): Extend to handle .zip extension.

import: Add GNU importer.

Suggested by Karl Berry <karl@gnu.org>
and Andreas Enge <andreas@enge.fr>.

* guix/import/gnu.scm, guix/scripts/import/gnu.scm: New files.
* Makefile.am (MODULES): Add them.
* guix/scripts/import.scm (importers): Add "gnu".
* guix/gnu-maintenance.scm (gnu-release-archive-types): New procedure.
  (download-tarball): Export.

gnu-maintenance: Introduce <gnu-release> data type.

* guix/gnu-maintenance.scm (<gnu-release>): New record type.
  (release-file): Rename to...
  (release-file?): ... this.  Return a Boolean.
  (tarball->version, coalesce-releases): New procedures.
  (releases): Call 'coalesce-releases' on RESULT.  Return <gnu-release>
  objects instead of pairs.
  (latest-release): Likewise.
  (package-update-path): Adjust accordingly.
* gnu/packages.scm (check-package-freshness): Adjust accordingly.

Merge branch 'master' into core-updates

gnu-maintenance: Add missing type check.

* guix/gnu-maintenance.scm (gnu-package?): Only call 'mirror-type' when
  URL is a string.

gnu-maintenance: Avoid network access in 'gnu-package?'.

* guix/gnu-maintenance.scm (gnu-package?): Add 'mirror-type' procedure.
  Resort to 'official-gnu-packages' only when 'mirror-type' returns #f.

Merge branch 'master' into core-updates

gnu-maintenance: Adjust 'latest-release' to filter Bash's patch directories.

* guix/gnu-maintenance.scm (latest-release)[patch-directory-name?]: New
  procedure.
  <subdirs>: Use it to filter out Bash-like patch directories.

gnu-maintenance: Ignore "redirect" blurbs.

* guix/gnu-maintenance.scm (official-gnu-packages)[official-description]:
  Return #f for blurbs that start with "redirect ".

Merge branch 'master' into core-updates

gnu-maintenance: Adjust URL of package description file.

* guix/gnu-maintenance.scm (%package-description-url): Adjust to the
  new URL.

gnu-maintenance: Get descriptions from 'gnumaint/pkgdescr.txt'.

* guix/gnu-maintenance.scm (%gnumaint-base-url): New variable.
  (%package-list-url): Use it.
  (%gsrc-package-list-url): Remove.
  (%package-description-url): New variable.
  (official-gnu-packages): Change to use %PACKAGE-DESCRIPTION-URL
  instead of %GSRC-PACKAGE-LIST-URL.  Adjust recutils field names
  accordingly.

Rename (guix web) to (guix http-client).

* guix/web.scm: Rename to...
* guix/http-client.scm: ... this.
* guix/gnu-maintenance.scm, guix/scripts/substitute-binary.scm,
  Makefile.am, po/POTFILES.in: Update accordingly.

guix package: Reuse FTP connections for subsequent `latest-release' calls.

* guix/gnu-maintenance.scm (latest-release): Add `ftp-close' and
  `ftp-open' keyword parameters.
* guix/scripts/package.scm (ftp-open*): New variable.
  (check-package-freshness): Call `latest-release' with `ftp-open*' and
  a no-op procedure.

gnu-maintenance: `latest-release' closes its connection.

* guix/gnu-maintenance.scm (latest-release): Close CONN before
  returning.

gnu-maintenance: Add `doc-description' field to <gnu-package-descriptor>.

* guix/gnu-maintenance.scm (%gsrc-package-list-url): New variable.
  (<gnu-package-descriptor>): Add `doc-description' field.
  (official-gnu-packages)[group-package-fields]: Rename to...
  [read-records]: ... this.  Reverse the result.
  [gsrc-description]: New procedure.
  Add the "description" field to the alist passed to `alist->record'.

gnu-maintenance: Use `recutils->alist'.

* guix/gnu-maintenance.scm (official-gnu-packages)[group-package-fields]:
  Rewrite in terms of `recutils->alist'.  Remove `state' parameter.
  Specify "doc-url" and "language" as multiple-value keys in the
  `alist->record' call.

guix refresh: Add '--key-download'.

* guix/gnu-maintenance.scm (download-tarball): Add a 'key-download'
  keyword argument and pass it to 'gnupg-verify*'.  Make
  'archive-type' a keyword argument.
  (package-update): Add a 'key-download' keyword argument.  Pass
  'archive-type' and 'key-download' keyword arguments to
  'download-tarball'.

* guix/gnupg.scm: Import (ice-9 i18n) and (guix ui).
  (gnupg-verify*): Add a 'key-download' keyword argument and adjust
  'gnupg-verify*' to use it.  Make 'server' a keyword argument.

* guix/scripts/refresh.scm (show-help, %options): Add and document
  '--key-download'.
  (update-package): Add a 'key-download' keyword argument and pass it
  to 'package-update'.
  (guix-refresh): Pass 'key-download' to 'update-package'.  Limit
  lines to a maximum of 79 characters.

Move record utilities to (guix records).

* guix/utils.scm (define-record-type*): Move to...
* guix/records.scm: ... here.  New file.
* guix/build-system.scm, guix/packages.scm: Use it.
* guix/gnu-maintenance.scm: Likewise.
  (official-gnu-packages)[alist->record]: Remove.
* guix/scripts/substitute-binary.scm: Likewise.
  (alist->record, object->fields): Remove.
* tests/utils.scm ("define-record-type*", "define-record-type* with
  letrec* behavior", "define-record-type* & inherit",
  "define-record-type* & inherit & letrec* behavior",
  "define-record-type* & thunked", "define-record-type* & thunked &
  default", "define-record-type* & thunked & inherited"): Move to...
* tests/records.scm: ... here.  New file.

gnu-maintenance: Add GnuTLS FTP server.

* guix/gnu-maintenance.scm (ftp-server/directory)[quirks]: Add GnuTLS.