Merge branch 'core-updates'

substitute-binary: Support decompression from non-file ports.

* guix/scripts/substitute-binary.scm (filtered-port): Move to utils.scm.
  (decompressed-port): Upon "none", return '() as the second value.
  (guix-substitute-binary): Expect `decompressed-port' to return a list
  of PIDs as its second value.
* guix/utils.scm (filtered-port): New procedure.  Add case for when
  INPUT is not `file-port?'.
* tests/utils.scm ("filtered-port, file", "filtered-port, non-file"):
  New tests.

guix package: Add `--search-paths' & co.

* guix/scripts/package.scm (search-path-environment-variables,
  display-search-paths): New procedures.
  (show-help, %options): Add `--search-paths'.
  (guix-package)[process-actions]: Call `display-search-paths' once the
  profile is ready.
  [process-query]: Honor `search-paths'.

utils: Add `string-tokenize*'.

* guix/utils.scm (string-tokenize*): New procedure.
* tests/utils.scm ("string-tokenize*"): New test.

Merge branch 'master' into core-updates

Conflicts:
	Makefile.am
	gnu/packages/autotools.scm
	gnu/packages/guile.scm
	gnu/packages/python.scm
	gnu/packages/shishi.scm
	guix/gnu-maintenance.scm
	guix/scripts/build.scm
	guix/scripts/gc.scm
	guix/scripts/package.scm
	guix/scripts/substitute-binary.scm
	guix/ui.scm
	nix/nix-daemon/guix-daemon.cc
	test-env.in
	tests/nar.scm
	tests/store.scm

packages: Use `read' and source properties for `package-field-location'.

* guix/packages.scm (package-field-location): Rewrite using `read' and
  source properties.  Change to return #f upon failure.
* tests/packages.scm ("package-field-location"): Check for #f upon failure.
* build-aux/sync-synopses.scm: Adjust accordingly.

packages: Add `package-field-location'.

* guix/packages.scm (package-field-location): New procedure.
* build-aux/sync-synopses.scm: Use it instead of `package-location'.
* tests/packages.scm ("package-field-location"): New test.

tests: Use a new synopsis of GNU Hello.

* tests/guix-package.sh: Use a new synopsis of GNU Hello, which was
  added in f50d2669e3e624365221cc81918ba55fdce94107.

scripts: Report what will be substituted.

* guix/derivations.scm (derivation-input-output-paths): New procedure.
  (derivation-prerequisites-to-build): New `use-substitutes?' keyword
  argument.  Change two return the list of substitutable paths as a
  second argument.
* guix/ui.scm (show-what-to-build): Turn `dry-run?' into a keyword
  argument.  New `use-substitutes?' keyword argument.  Use `fold2' and
  adjust to use both return values of
  `derivation-prerequisites-to-build'.  Display what will/would be
  downloaded.
* guix/scripts/build.scm (guix-build): Adjust accordingly.
* guix/scripts/package.scm (guix-package): Likewise.
* tests/derivations.scm ("derivation-prerequisites-to-build and
  substitutes"): New test.

substitute-binary: Add a local cache.

* guix/scripts/substitute-binary.scm (%narinfo-cache-directory,
  %narinfo-ttl, %narinfo-negative-ttl): New variables.
  (with-atomic-file-output, object->fields, read-narinfo,
  write-narinfo, narinfo->string, string->narinfo, lookup-narinfo): New
  procedures.
  (fetch-narinfo): Adjust to use `read-narinfo'.
  (guix-substitute-binary): Ensure the existence of
  %NARINFO-CACHE-DIRECTORY.  Use `lookup-narinfo' instead of
  `fetch-narinfo'.

utils: Add `fold2'.

* gnu/packages.scm (fold2): Remove.
* guix/utils.scm (fold2): New procedure.  Generalization of the above to
  one and two lists.
* tests/utils.scm ("fold2, 1 list", "fold2, 2 lists"): New tests.

substitute-binary: Implement `--substitute'.

This allows build outputs to be transparently downloaded from
http://hydra.gnu.org, for example.

* config-daemon.ac: Check for `gzip', `bzip2', and `xz'.
* guix/config.scm.in (%gzip, %bzip2, %xz): New variable.
* guix/scripts/substitute-binary.scm (fetch): Return SIZE as a second value.
  (<narinfo>): Change `url' to `uri'.
  (make-narinfo): Rename to...
  (narinfo-maker): ... this.  Handle relative URLs.
  (fetch-narinfo): Adjust accordingly.
  (filtered-port, decompressed-port): New procedures.
  (guix-substitute-binary): Implement the `--substitute' case.
* tests/store.scm ("substitute query"): Use (%store-prefix) instead
  of (getenv "NIX_STORE_DIR").
  ("substitute"): New test.

nar: Add support for symlinks.

* guix/nar.scm (write-file): Add case for type `symlink'.
  (restore-file): Likewise.
* tests/nar.scm (random-file-size, make-file-tree, delete-file-tree,
  with-file-tree, file-tree-equal?, make-random-bytevector,
  populate-file): New procedures.
  (%test-dir): New variable.
  ("write-file + restore-file"): Use `%test-dir' and `file-tree-equal?'.
  ("write-file + restore-file with symlinks"): New test.

nar: Implement restoration from Nar.

* guix/nar.scm (&nar-error, &nar-read-error): New condition types.
  (dump): New procedure.
  (write-contents)[dump]: Remove.  Use the one above instead.
  (read-contents, write-file, restore-file): New procedures.
  (%archive-version-1): New variable.

Add preliminary binary substituter.

* guix/scripts/substitute-binary.scm: New file.
* Makefile.am (MODULES): Add it.
* nix/scripts/substitute-binary.in: New file.
* config-daemon.ac: Produce nix/scripts/substitute-binary.
* daemon.am (nodist_pkglibexec_SCRIPTS): Add
  nix/scripts/substitute-binary.
* guix/store.scm (substitutable-path-info): Use the
  `query-substitutable-path-infos' RPC.
* nix/nix-daemon/guix-daemon.cc (main): Honor `NIX_SUBSTITUTERS'.
* pre-inst-env.in: Set `NIX_SUBSTITUTERS'.
* test-env.in: Leave `NIX_SUBSTITUTERS' unchanged.  Set
  `GUIX_BINARY_SUBSTITUTE_URL, and create
  $NIX_STATE_DIR/substituter-data.
  Run `guix-daemon' within `./pre-inst-env'.
* tests/store.scm ("substitute query"): New test.

store: Add `store-path-hash-part'.

* guix/store.scm (store-path-hash-part): New procedure.
* tests/store.scm ("store-path-hash-part", "store-path-hash-part #f"):
  New tests.

tests: Remove temporary directory created by nar.scm.

* tests/nar.scm ("write-file + restore-file with symlinks"): Add (rm-rf
  output).

substitute-binary: Implement `--substitute'.

This allows build outputs to be transparently downloaded from
http://hydra.gnu.org, for example.

* config-daemon.ac: Check for `gzip', `bzip2', and `xz'.
* guix/config.scm.in (%gzip, %bzip2, %xz): New variable.
* guix/scripts/substitute-binary.scm (fetch): Return SIZE as a second value.
  (<narinfo>): Change `url' to `uri'.
  (make-narinfo): Rename to...
  (narinfo-maker): ... this.  Handle relative URLs.
  (fetch-narinfo): Adjust accordingly.
  (filtered-port, decompressed-port): New procedures.
  (guix-substitute-binary): Implement the `--substitute' case.
* tests/store.scm ("substitute query"): Use (%store-prefix) instead
  of (getenv "NIX_STORE_DIR").
  ("substitute"): New test.

nar: Add support for symlinks.

* guix/nar.scm (write-file): Add case for type `symlink'.
  (restore-file): Likewise.
* tests/nar.scm (random-file-size, make-file-tree, delete-file-tree,
  with-file-tree, file-tree-equal?, make-random-bytevector,
  populate-file): New procedures.
  (%test-dir): New variable.
  ("write-file + restore-file"): Use `%test-dir' and `file-tree-equal?'.
  ("write-file + restore-file with symlinks"): New test.

tests: Adjust `gnu-build' test to search path mechanism.

Fixes a regression introduced in a18eda2.
Reported by Nikita Karetnikov <nikita@karetnikov.org>.

* tests/builders.scm (%bootstrap-search-paths): New variable.
  ("gnu-build"): Pass #:search-paths.