import: hackage: Remove reference to unbound variable.

* guix/scripts/import/hackage.scm (guix-import-hackage): Fix error message for
  imports from stdin, which referred to unbound variable 'package-name'.

size: Remove leftover 'pk'.

* guix/scripts/size.scm (profile->page-map): Remove leftover 'pk'.

publish: Do not load archive content in memory.

Previously, before replying to a /nar/* request, 'guix publish' would first
build up the whole nar into memory (as a consequence of
<http://bugs.gnu.org/21093>), which obviously doesn't scale.

* guix/scripts/publish.scm (render-nar): Return STORE-PATH instead of a
  procedure that calls 'write-file'.
  (sans-content-length): New procedure.
  (http-write): For 'x-nix-archive', don't call '%http-write'.  Instead, call
  'write-file' right from here, using BODY as the file name.

Merge branch 'master' into core-updates

publish: Serve /nar requests in a separate thread.

* guix/scripts/publish.scm (%http-write): New variable.
  (http-write): New procedure.
  (concurrent-http-server): New variable.
  (run-publish-server): Use it.

publish: Write hashes in nix-base32 format.

* guix/scripts/publish.scm (narinfo-string): Use
  'bytevector->nix-base32-string', not 'bytevector->base32-string'.

system: Add 'kernel-arguments' field.

* gnu/system.scm (<operating-system>)[kernel-arguments]: New field.
  (operating-system-grub.cfg): Honor it.
  (operating-system-parameters-file): Add 'kernel-arguments' to the parameters
  file.
* guix/scripts/system.scm (previous-grub-entries)[system->grub-entry]: Read
  the 'kernel-arguments' field of the parameters file, when available.
* gnu/system/vm.scm (system-qemu-image/shared-store-script):
  Use (operating-system-kernel-arguments os) in '-append'.
* doc/guix.texi (operating-system Reference): Document it.

size: Gracefully handle EPIPE.

* guix/scripts/size.scm (guix-size): Wrap body in 'leave-on-EPIPE'.

ui: Add 'leave-on-EPIPE'.

* guix/scripts/package.scm (leave-on-EPIPE): Move to...
* guix/ui.scm (leave-on-EPIPE): ... here.

Merge branch 'master' into core-updates

substitute: Improve functional decomposition.

* guix/scripts/substitute.scm (display-narinfo-data,
  process-query, process-substitution): New procedures.  Code moved from...
  (guix-substitute): ... here.  Use them.

guix build: Add '--substitute-urls' client option.

* guix/scripts/build.scm (%standard-build-options,
  show-build-options-help): Add --substitute-urls=URLS.
  (set-build-options-from-command-line): Honor it.
* guix/store.scm (%default-substitute-urls): Make public.
* doc/guix.texi (Substitutes): Add xref to the client --substitute-urls
  option.
  (Invoking guix build): Document it.
  (Invoking guix-daemon): Add 'daemon-substitute-urls' anchor.

substitute: Honor "substitute-urls" option passed by "untrusted" clients.

* guix/scripts/substitute.scm (or*): New macro.
  (%cache-url): Honor "untrusted-substitute-urls".
* guix/tests.scm (%test-substitute-urls): New variable.
  (open-connection-for-tests): Use it.
* tests/derivations.scm ("derivation-prerequisites-to-build and substitutes",
  "derivation-prerequisites-to-build and substitutes, non-substitutable
  build", "derivation-prerequisites-to-build and substitutes, local build"):
  Pass it to 'set-build-options'.
* tests/guix-daemon.sh: Likewise.
* tests/store.scm ("substitute query, alternating URLs"): New test.
  ("substitute query", "substitute", "substitute + build-things with output
  path", "substitute, corrupt output hash", "substitute --fallback"): Pass
  #:substitute-urls to 'set-build-options'.

substitute: Store cached narinfo in cache-specific sub-directories.

This ensures that switching between different substitute servers doesn't lead
to a polluted narinfo cache.

* guix/scripts/substitute.scm (narinfo-cache-file): Add 'cache-url'
  parameter.  Add the base32 of CACHE-URL as a sub-directory under
  %NARINFO-CACHE-DIRECTORY.  Update callers.
  (cached-narinfo): Likewise.  Call 'mkdir-p' on the dirname of the cache
  file.  Update callers.
  (remove-expired-cached-narinfos): Add 'directory' parameter and use it
  instead of %NARINFO-CACHE-DIRECTORY.
  (narinfo-cache-directories): New procedure.
  (maybe-remove-expired-cached-narinfo): Call 'remove-expired-cached-narinfos'
  for each item returned by 'narinfo-cache-directories'.

substitute: Pass the cache URL instead of <cache> objects.

* guix/scripts/substitute.scm (<cache>): Rename to...
  (<cache-info>): ... this.
  (open-cache): Rename to...
  (download-cache-info): ... this.  Return a <cache-info> or #f.
  (open-cache*): Remove.
  (cache-narinfo!): Take a URL instead of a <cache> as the first parameter.
  (fetch-narinfos): Likewise.  Call 'download-cache-info'.  Remove use of
  'force'.
  (guix-substitute): Replace calls to 'open-cache*' with %CACHE-URL.

substitute: Remove unneeded conditionals.

* guix/scripts/substitute.scm (guix-substitute): Remove unneeded (if cache
  ...) forms since CACHE is always true (it's a promise.)

guix lint: Remove duplicated module lines.

* guix/scripts/lint.scm (guix): Remove duplicated lines for using
  'srfi-34' and 'srfi-35' modules.  These lines were introduced twice by
  commits b210b35 and 002c57c.

offload: Add 'ssh-options' field to <build-machine>.

* guix/scripts/offload.scm (<build-machine>)[ssh-options]: New field.
  (remote-pipe): Use it.
  (send-files): Likewise.

import: Add 'elpa' importer.

* guix/import/elpa.scm: New file.
* guix/scripts/import.scm: Add "elpa" to 'importers'.
* guix/scripts/import/elpa.scm: New file.
* Makefile.am (MODULES): Add 'guix/import/elpa.scm' and
  'guix/scripts/import/elpa.scm'.
  (SCM_TESTS): Add 'tests/elpa.scm'.
* doc/guix.texi (Invoking guix import): Document it.
* tests/elpa.scm: New file.
* po/guix/POTFILES.in: Add 'guix/scripts/import/elpa.scm'.

gnu: system: Move <file-system-mapping> into (gnu system file-systems).

* gnu/system/vm.scm (<file-system-mapping>, %store-mapping): Move from here...
* gnu/system/file-systems.scm: ...to here.
* guix/scripts/system.scm: Import (gnu system file-systems).