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'.

store: Add 'log-file' procedure.

* guix/store.scm (log-file): New procedure.
* tests/store.scm ("log-file, derivation", "log-file, output file
  name"): New tests.

packages: Add a 'snippet' field to <origin>.

* guix/packages.scm (<origin>): Add 'snippet', 'modules', and
  'imported-modules' fields.
  (patch-and-repack): Make 'inputs' a keyword parameter.  Add 'snippet',
  'modules', and 'imported-modules' parameters.  Accept SOURCE as a raw
  file name.  Insert SNIPPET in BUILDER.  Pass IMPORTED-MODULES to
  'build-expression->derivation'.
  (package-source-derivation): Pass the extra arguments to
  'patch-and-repack'.
* tests/packages.scm ("package-source-derivation, snippet"): New test.
* doc/guix.texi (Defining Packages): Mention the 'patches' and 'snippet'
  fields.
  (Invoking guix build): Tell that --source has patches and snippets
  applied.
  (Software Freedom): Mention packages that contain non-free code.

tests: Fix max-silent-time test.

* tests/derivations.scm ("build-expression->derivation and
  max-silent-time"): Use STORE instead of %STORE.  Change BUILDER to
  succeed by default.  Return #f when no exception is raised.

tests: Add the builder as an input to raw derivations.

* tests/derivations.scm ("build derivation with 1 source",
  "derivation with local file as input",
  "derivation with a fixed-output input",
  "multiple-output derivation",
  "multiple-output derivation, non-alphabetic order",
  "user of multiple-output derivation"): Add %BASH as an input, needed
  in chroot builds.

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.

ui: Factorize package specification parsing.

* guix/ui.scm (package-specification->name+version+output): New
  procedure.
* guix/scripts/package.scm (specification->package+output): Use it.
* tests/ui.scm ("package-specification->name+version+output"): New test.

derivations: 'derivation-path->output-path' honors the 'output' parameter.

* guix/derivations.scm (derivation-path->output-path): Pass OUTPUT.
* tests/derivations.scm ("multiple-output derivation,
  derivation-path->output-path"): New test.

records: define-record-type*: Field bindings are bound with 'let*'.

* guix/records.scm (define-record-type*): Wrap field bindings in a
  'let*', not in a 'letrec*', which turned out to be pointlessly
  inconvenient.
* tests/records.scm: Adjust test names accordingly.

monads: Allow resolution of a monad's bind/return at expansion time.

* guix/monads.scm (<monad>): Turn in a raw SRFI-9 record type.
  (define-monad): New macro.
  (with-monad): Add a case for when MONAD is a macro.
  (identity-return, identity-bind, store-return, store-bind): Inline.
  (%identity-monad, %store-monad): Use 'define-monad'.
* tests/monads.scm ("monad?"): New test.

Add (guix monads).

* guix/monads.scm: New file.
* tests/monads.scm: New file.
* Makefile.am (MODULES): Add guix/monads.scm.
  (SCM_TESTS): Add tests/monads.scm.
* doc/guix.texi (The Store Monad): New node.
  (The Store): Reference it.

guix package: '--delete-generations' deletes generations older than specified.

* guix/scripts/package.scm (matching-generations): Add
  'duration-relation' keyword parameter.
  (guix-package)[process-action](delete-generations): Pass
  #:duration-relation >.
* tests/guix-package.sh: Add test.
* doc/guix.texi (Invoking guix package): Clarify the meaning of
  durations for '--list-durations' and '--delete-durations'.

tests: Fix typo.

* tests/guix-package.sh: Add missing "-p" option.

build-system/trivial: Take the 'source' field into account.

* guix/build-system/trivial.scm (trivial-build): When SOURCE is true,
  add it to INPUTS.
  (trivial-cross-build): Likewise.
* tests/packages.scm ("trivial with source"): New test.

guix package: Add '--delete-generations'.

* guix/scripts/package.scm (switch-to-previous-generation): New function.
  (roll-back): Use the new function instead of 'switch-link'.
  (show-help): Add '--delete-generations'.
  (%options): Likewise.
  (guix-package)[process-actions]: Add 'current-generation-number',
  'display-and-delete', and 'delete-generation'.  Add support for
  '--delete-generations', and reindent the code.
* tests/guix-package.sh: Test '--delete-generations'.
* doc/guix.texi (Invoking guix-package): Document '--delete-generations'.

Merge branch 'master' into core-updates

guix package: Show which generation is the current one.

* guix/scripts/package.scm (guix-package)[process-query]: Show that a
  generation is the current one if the profile points to it.
* tests/guix-package.sh: Test it.

tests: Use 'test -z' to check that a string equals zero.

guix package: Do not list the zeroth generation.

* guix/scripts/package.scm (guix-package)[process-query]: Change
  'list-generation' to not list the zeroth generation.
* tests/guix-package.sh: Test it.
* doc/guix.texi (Invoking guix package): Document it, and use the
  right term when talking about generations.

guix package: Exit with 1 when a generation cannot be listed.

* guix/scripts/package.scm (guix-package)[process-query]: Exit with 1
  when a generation does not exist or the profile points to the zeroth
  generation.
* tests/guix-package.sh: Test the former case.