* guix/utils.scm (package-name->name+version): New procedure.
* guix-package.in (guix-package)[find-package]: Use it.
* tests/utils.scm ("package-name->name+version"): New test.
* Makefile.am (.scm.go): Define $NIX_INSTANTIATE.
(TESTS_ENVIRONMENT): Likewise, and define $NIX_HASH.
* guix/utils.scm (nixpkgs-derivation): Use $NIX_INSTANTIATE when
defined.
* tests/utils.scm (%nix-hash): New variable.
("sha256 & bytevector->nix-base32-string"): Use it.
* guix/utils.scm (define-record-type*)[make-syntactic-constructor]: Bind
all the ((FIELD VALUE) ...) in a `letrec*'. Adjust `field-value'
accordingly.
* tests/utils.scm ("define-record-type* with letrec* behavior"): New
test.
* guix/utils.scm (gnu-triplet->nix-system): New procedure.
(%current-system): New variable.
* tests/utils.scm ("gnu-triplet->nix-system"): New test.
* tests/derivations.scm (%current-system): Remove. Update users to
use (%current-system) instead.
* guix/utils.scm (bytevector-quintet-ref-right,
bytevector-quintet-fold): New procedures.
(bytevector-quintet-fold-right): Add `quintet-fold' parameter; use it
instead of `bytevector-quintet-fold'.
(bytevector->base32-string): Pass BYTEVECTOR-QUINTET-FOLD as the
first parameter.
(bytevector->nix-base32-string): Pass BYTEVECTOR-QUINTET-FOLD-RIGHT as
the first parameter.
* tests/utils.scm ("sha256 & bytevector->nix-base32-string"): New test.