guix build: Improve procedural decomposition.

* guix/scripts/build.scm (%store): Remove.
  (derivation-from-expression): Add 'store' parameter.  Adjust caller
  accordingly.
  (register-root): New procedure, formerly within 'guix-build'.
  (options->derivations): New procedure, formerly inline within
  'guix-build'.
  (guix-build): Adjust accordingly.

Factorize package search between 'guix package' and 'guix build'.

* guix/scripts/package.scm (newest-available-packages): Remove.
  (find-best-packages-by-name): Move to...
* gnu/packages.scm (find-best-packages-by-name): ... here.
  (find-newest-available-packages): Memoize.
* guix/scripts/build.scm (specification->package): New procedure,
  formerly called 'find-package' within 'guix-build'.
  (guix-build): Adjust accordingly.

daemon: Implement signed archive import/export.

* guix/scripts/authenticate.scm, nix/scripts/guix-authenticate.in,
  tests/signing-key.pub, tests/signing-key.sec: New files.
* po/POTFILES.in: Add 'guix/scripts/authenticate.scm'.
* guix/store.scm (dump-port): New procedure.
  (process-stderr): Add 'user-port' optional parameter.  Handle
  the %STDERR-WRITE and %STDERR-READ cases as expected.
  (import-paths, export-path, export-paths): New procedures.
* tests/store.scm ("export/import several paths", "import corrupt
  path"): New tests.
* Makefile.am (MODULES): Add 'guix/scripts/authenticate.scm'.
  (EXTRA_DIST): Add 'tests/signing-key.{pub,sec}'.
* daemon.am (libstore_a_CPPFLAGS)[-DNIX_CONF_DIR]: Change 'NIX_CONF_DIR'
  to .../guix.  Change 'OPENSSL_PATH' to 'guix-authenticate'.
* config-daemon.ac: Instantiate 'nix/scripts/guix-authenticate'.
* nix/nix-daemon/guix-daemon.cc (main): Augment $PATH to include
  'settings.nixLibexecDir'.
* test-env.in: Export 'NIX_CONF_DIR' and 'NIX_LIBEXEC_DIR'.  Populate
  $NIX_CONF_DIR.

pull: Move build code to (guix build pull).

* guix/build/pull.scm: New file.
* Makefile.am (MODULES): Add it.
* guix/scripts/pull.scm (unpack): Use it.

guix package: allow multiple arguments after -i, -r, and -u.

* guix/scripts/package.scm (%options): Adapt option processors to accept and
  return a second seed value: 'arg-handler', which handles bare arguments (if
  not false).  The install, remove, and upgrade option processors return an
  arg-handler that repeat the same operation.  All other option processors
  return #f as the arg-handler.  Make the arguments to install and remove
  optional.  The upgrade option processor deletes (upgrade . #f) from the
  alist before adding a new entry.
  (guix-package): Procedures passed to 'args-fold*' accept the new seed value
  'arg-handler'.  The 'operand-proc' uses 'arg-handler' (if not false).

* doc/guix.texi (Invoking guix package): Update docs.

* tests/guix-package.sh: Add test.

pull: Compile guix/ files before gnu/ files.

* guix/scripts/pull.scm (unpack)[builder]: Build files under guix/
  before files under gnu/.

pull: Compile files in parallel.

* guix/scripts/pull.scm (unpack)[builder](compile-file*): Remove.
  (call-with-process, p-for-each): New procedures.  Use them to compile
  files in parallel.

pull: Limit memory usage when compiling.

Reported by Arne Babenhauserheide <arne.babenhauserheide@kit.edu>.

* guix/scripts/pull.scm (unpack)[builder](compile-file*): Change to run
  'compile-file' in a child process.  This limits memory usage; before
  that memory usage was proportional to the number of files to compile.

derivations: Use more keyword parameters for 'build-expression->derivation'.

* guix/derivations.scm (build-expression->derivation): Turn 'system' and
  'inputs' into keyword parameters.
  Adjust callers accordingly.
* gnu/system/linux.scm, gnu/system/vm.scm, guix/build-system/cmake.scm,
  guix/build-system/gnu.scm, guix/build-system/perl.scm,
  guix/build-system/python.scm, guix/build-system/trivial.scm,
  guix/download.scm, guix/packages.scm, guix/profiles.scm,
  guix/scripts/pull.scm, tests/derivations.scm, tests/guix-build.sh,
  tests/monads.scm, tests/store.scm, tests/union.scm: Adjust users of
  'build-expression->derivation' and 'derivation-expression'
  accordingly.
* doc/guix.texi (Derivations): Adjust 'build-expression->derivation'
  documentation accordingly.
  (The Store Monad): Likewise for 'derivation-expression'.

substitute-binary: Work around Guile 2.0.5's broken 'n-par-map'.

* guix/scripts/substitute-binary.scm (n-par-map*): New procedure.
  (guix-substitute-binary): Use it instead of 'n-par-map'.
  Reported by Nikita Karetnikov and Eric Bavier.

guix package: Honor the current output when upgrading.

* guix/scripts/package.scm (specification->package+output): Pass OUTPUT
  to 'package-specification->name+version+output'.

Merge branch 'master' into core-updates

Conflicts:
	guix/packages.scm

guix build: '-e' can be passed a monadic thunk.

* guix/ui.scm (read/eval): New procedure.
  (read/eval-package-expression): Use it.
* guix/scripts/build.scm (derivations-from-package-expressions): Rename to...
  (derivation-from-expression): ... this.  Accept procedures, under the
  assumption that they are monadic thunk.
  (show-help): Adjust accordingly.
  (guix-build): Ditto.
* tests/guix-build.sh: Add test.
* doc/guix.texi (Invoking guix build): Augment description of '-e'.

substitute-binary: Adjust timeout handling for Guile > 2.0.9.

* guix/scripts/substitute-binary.scm (with-timeout): Update comment to
  mention the fix's commit ID.
  (fetch): In the 'with-timeout' handler, close PORT only one Guile
  versions < 2.0.9.39.  Before that, on Guile >= 2.0.9.39, the HTTP
  client would end up trying to read from a closed file descriptor.

guix build: Add '--log-file'.

* guix/scripts/build.scm (show-help): Add '--log-file'.
  (%options): Likewise.
  (guix-build): Set %FILE-PORT-NAME-CANONICALIZATION.  Honor '--log-file'.
* tests/guix-build.sh: Add '--log-file' tests.
* doc/guix.texi (Invoking guix build): Document '--log-file'.

substitute-binary: Increase lookup concurrency to reduce latency.

* guix/scripts/substitute-binary.scm (%lookup-threads): New variable.
  (guix-substitute-binary): Use 'n-par-map' instead of 'par-map' for
  batch 'lookup-narinfo' calls.

Merge branch 'master' into core-updates

Conflicts:
	guix/packages.scm

guix package: Show the output name of what's being removed.

* guix/scripts/package.scm (show-what-to-remove/install): Show the
  output name of packages being removed.

guix package: Fix indentation of "will be removed" messages.

* guix/scripts/package.scm (show-what-to-remove/install): Remove extra
  indentation from the removal sentences.

guix package: Allow removal of a specific package output.

Fixes <http://bugs.gnu.org/15756>.

* guix/profiles.scm (<manifest-pattern>): New record type.
  (remove-manifest-entry): Remove.
  (entry-predicate, manifest-matching-entries): New procedures.
  (manifest-remove): Accept a list of <manifest-pattern>.
  (manifest-installed?): Replace 'name' parameter by 'pattern', a
  <manifest-pattern>.
* guix/scripts/package.scm (options->removable): Return a list of
  <manifest-pattern>.
  (guix-package)[process-action]: Use 'manifest-matching-entries' to
  compute the list of packages to remove.
* tests/profiles.scm: New file.
* Makefile.am (SCM_TESTS): Add it.