Move `sha256' to (guix utils).

* guix/derivations.scm (sha256): Move to...
* guix/utils.scm (sha256): ... here.

guix/derivations.scm

@@ -25,9 +25,6 @@
   #:use-module (ice-9 match)
   #:use-module (ice-9 rdelim)
   #:use-module (guix store)
-  #:use-module ((chop hash)
-                #:select (bytevector-hash
-                          hash-method/sha256))
   #:export (derivation?
             derivation-outputs
             derivation-inputs
@@ -187,9 +184,6 @@ that form."
                       env-vars))
      (display ")" port))))
 
-(define (sha256 bv)
-  "Return the SHA256 of BV as a bytevector."
-  (bytevector-hash hash-method/sha256 bv))
 
 (define (derivation-hash drv)      ; `hashDerivationModulo' in derivations.cc
   "Return the hash of DRV, modulo its fixed-output inputs, as a bytevector."

guix/utils.scm

@@ -19,9 +19,13 @@
 (define-module (guix utils)
   #:use-module (srfi srfi-60)
   #:use-module (rnrs bytevectors)
+  #:use-module ((chop hash)
+                #:select (bytevector-hash
+                          hash-method/sha256))
   #:export (bytevector-quintet-length
             bytevector->base32-string
-            bytevector->nix-base32-string))
+            bytevector->nix-base32-string
+            sha256))
 
 (define bytevector-quintet-ref
   (let* ((ref  bytevector-u8-ref)
@@ -98,3 +102,12 @@ the previous application or INIT."
 
 (define bytevector->nix-base32-string
   (make-bytevector->base32-string %nix-base32-chars))
+
+;;;
+;;; Hash.
+;;;
+
+(define (sha256 bv)
+  "Return the SHA256 of BV as a bytevector."
+  (bytevector-hash hash-method/sha256 bv))
+