ui: Add a `warning' macro.

* guix/ui.scm (program-name, guix-warning-port): New variables.
  (warning): New macro.
  (guix-main): Parametrize PROGRAM-NAME.
* guix/scripts/build.scm, guix/scripts/download.scm,
  guix/scripts/gc.scm, guix/scripts/package.scm: Adjust to use `leave'
  and `warning' consistently.

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 (guix nar) and (guix serialization).

* guix/store.scm (write-int, read-int, write-long-long, read-long-long,
  write-padding, write-string, read-string, read-latin1-string,
  write-string-list, read-string-list, write-store-path,
  read-store-path, write-store-path-list, read-store-path-list): Move to
  serialization.scm.
  (write-contents, write-file): Move to nar.scm.
* guix/nar.scm, guix/serialization.scm: New files.
* Makefile.am (MODULES): Add them.

substitute-binary: Fix communication of several store paths to the daemon.

* guix/scripts/substitute-binary.scm (guix-substitute-binary)["--query"]:
  Emit blank lines only after the complete list of store paths has been
  returned.

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.

gnu-maintenance: Adjust `http-fetch' to the various Guile versions.

* guix/gnu-maintenance.scm (http-fetch): Try #:streaming? #t, or
  'http-get*', or 'http-get' as a last resort.  Check whether DATA is
  #f, a string, or an input port.

pull: Switch to the cgit URL.

* guix/scripts/pull.scm (%snapshot-url): Switch to the cgit URL, given
  that the Hydra one is not currently available.

snix: Adjust import to current Nixpkgs input attribute names.

* guix/snix.scm (snix-derivation->guix-package): Use the new names
  `nativeBuildInputs' and `propagatedNativeBuildInputs'.

gnu-maintenance: Improve 'official-gnu-packages'; add related procedures.

* guix/gnu-maintenance.scm (http-fetch): Return an input port.
  (<gnu-package-descriptor>): Add it.
  (official-gnu-packages): Use <gnu-package-descriptor>.
  (find-packages): Add it.
  (gnu-package?): Adjust accordingly.

Add (guix build-system cmake).

* guix/build/cmake-build-system.scm, guix/build-system/cmake.scm: New files.
* Makefile.am (MODULES): Add them.

download: Remove unreliable GNU mirror.

* guix/download.scm (%mirrors)[gnu]: Remove ftp.chg.ru.

store: Really disable file name canonicalization for derivation inputs.

* guix/store.scm (write-contents)[call-with-binary-input-file]: Set
  %FILE-PORT-NAME-CANONICALIZATION to #f.
* gnu/packages.scm (search-patch, search-bootstrap-binary): Leave
  %FILE-PORT-NAME-CANONICALIZATION unchanged.  This reverts 9776ebb.

store: Use `sendfile' when available.

* guix/store.scm (write-contents)[call-with-binary-input-file]: New
  procedure.
  Use `sendfile' instead of `dump' when available.  Add `size'
  parameter.
  (write-file): Update caller.

guix package: Report packages to be removed/installed.

* guix/scripts/package.scm (guix-package)[process-actions](show-what-to-remove/install):
  New procedure.
  Call it before `show-what-to-build'.

derivations: Optimize `build-expression->derivation'.

This reduces the execution time of
"guix build -e '(@ (gnu packages emacs) emacs)' -d" by 6%, from
1.15s to 1.08s.

* guix/derivations.scm (build-expression->derivation): Write the builder
  as UTF-8.

derivations: Optimize `write-derivation'.

This reduces the execution time of
"guix build -e '(@ (gnu packages emacs) emacs)' -d" by 25%, from
1.54 s. to 1.15s.

* guix/derivations.scm (write-sequence, write-list, write-tuple): New
  procedures.
  (write-derivation)[list->string, write-list]: Remove.
  [write-string-list, write-output, write-input, write-env-var]: New helpers.
  Rewrite in terms of these new helpers.

guix package: Gracefully handle `official-gnu-packages' failure.

* guix/gnu-maintenance.scm (http-fetch): Error out when DATA is #f.
* guix/scripts/package.scm (check-package-freshness): Wrap
  `gnu-package?' call in `false-if-exception'.
  Reported by Cyril Roelandt <tipecaml@gmail.com>.

ui: Gracefully report failures to connect to the daemon.

* guix/store.scm (&nix-connection-error): New condition type.
  (open-connection): Translate `system-error' during the `connect' call
  into `&nix-connection-error'.
* guix/ui.scm (call-with-error-handling): Add case for `nix-connection-error?'.
* guix/scripts/package.scm (guix-package): Move `open-connection' call
  within `with-error-handling'.
* guix/scripts/pull.scm (guix-pull): Likewise.
* guix/scripts/download.scm (guix-download): Move body within
  `with-error-handling'.

packages: Remove the default value for `license'.

* guix/packages.scm (<package>): Remove the default value for `license'.
* gnu/packages/bootstrap.scm (package-from-tarball,
  %bootstrap-glibc, %bootstrap-gcc): Initialize `license'.
* tests/packages.scm (dummy-package): Likewise.