nar: Clarify that 'assert-valid-signature' accepts a string.

* guix/nar.scm (assert-valid-signature): Improve the wording.

diff --git a/guix/nar.scm b/guix/nar.scm
index 5bf1745..dfee309 100644 (file)
--- a/guix/nar.scm
+++ b/guix/nar.scm
@@ -369,8 +369,9 @@ while the locks are held."
     port)
 
   (define (assert-valid-signature signature hash file)
-    ;; Bail out if SIGNATURE, an sexp, doesn't match HASH, a bytevector
-    ;; containing the expected hash for FILE.
+    ;; Bail out if SIGNATURE, which must be a string as produced by
+    ;; 'canonical-sexp->string', doesn't match HASH, a bytevector containing
+    ;; the expected hash for FILE.
     (let* ((signature (catch 'gcry-error
                         (lambda ()
                           (string->canonical-sexp signature))