guix hash: Support several files.

* guix/scripts/hash.scm (guix-hash): Allow several files.
[file-hash]: Catch system-error.
[formatted-hash]: New procedure.
* tests/guix-hash.sh: Add test.
* doc/guix.texi (Invoking guix hash): Mention "one or more files".

Co-authored-by: Ludovic Courtès <ludo@gnu.org>

doc/guix.texi

@@ -11713,13 +11713,13 @@ store.
 @cindex @command{guix hash}
 The @command{guix hash} command computes the hash of a file.
 It is primarily a convenience tool for anyone contributing to the
-distribution: it computes the cryptographic hash of a file, which can be
+distribution: it computes the cryptographic hash of one or more files, which can be
 used in the definition of a package (@pxref{Defining Packages}).
 
 The general syntax is:
 
 @example
-guix hash @var{option} @var{file}
+guix hash @var{option} @var{file} ...
 @end example
 
 When @var{file} is @code{-} (a hyphen), @command{guix hash} computes the

guix/scripts/hash.scm

@@ -3,6 +3,7 @@
 ;;; Copyright © 2013 Nikita Karetnikov <nikita@karetnikov.org>
 ;;; Copyright © 2016 Jan Nieuwenhuizen <janneke@gnu.org>
 ;;; Copyright © 2018 Tim Gesthuizen <tim.gesthuizen@yahoo.de>
+;;; Copyright © 2021 Simon Tournier <zimon.toutoune@gmail.com>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -149,27 +150,35 @@ and 'base16' ('hex' and 'hexadecimal' can be used as well).\n"))
     (define (file-hash file)
       ;; Compute the hash of FILE.
       ;; Catch and gracefully report possible '&nar-error' conditions.
-      (with-error-handling
       (if (assoc-ref opts 'recursive?)
+          (with-error-handling
             (let-values (((port get-hash)
                           (open-hash-port (assoc-ref opts 'hash-algorithm))))
               (write-file file port #:select? select?)
               (force-output port)
-              (get-hash))
-            (match file
-              ("-" (port-hash (assoc-ref opts 'hash-algorithm)
-                              (current-input-port)))
-              (_   (call-with-input-file file
+              (get-hash)))
+          (catch 'system-error
+            (lambda _
+              (call-with-input-file file
                 (cute port-hash (assoc-ref opts 'hash-algorithm)
-                           <>)))))))
+                      <>)))
+            (lambda args
+              (leave (G_ "~a ~a~%")
+                     file
+                     (strerror (system-error-errno args)))))))
+
+    (define (formatted-hash thing)
+      (match thing
+        ("-" (with-error-handling
+               (fmt (port-hash (assoc-ref opts 'hash-algorithm)
+                               (current-input-port)))))
+        (_
+         (fmt (file-hash thing)))))
 
     (match args
-      ((file)
-       (catch 'system-error
-         (lambda ()
-           (format #t "~a~%" (fmt (file-hash file))))
-         (lambda args
-           (leave (G_ "~a~%")
-                  (strerror (system-error-errno args))))))
-      (x
-       (leave (G_ "wrong number of arguments~%"))))))
+      (()
+       (leave (G_ "no arguments specified~%")))
+      (_
+       (for-each
+        (compose (cute format #t "~a~%" <>) formatted-hash)
+        args)))))

tests/guix-hash.sh

@@ -34,6 +34,12 @@ test `guix hash -f base32 /dev/null` = 4oymiquy7qobjgx36tejs35zeqt24qpemsnzgtfes
 test `guix hash -H sha512 -f hex /dev/null` = cf83e1357eefb8bdf1542850d66d8007d620e4050b5715dc83f4a921d36ce9ce47d0d13c5d85f2b0ff8318d2877eec2f63b931bd47417a81a538327af927da3e
 test `guix hash -H sha1 -f base64 /dev/null` = "2jmj7l5rSw0yVb/vlWAYkK/YBwk="
 
+# Several files.
+test "`guix hash /dev/null "$abs_top_srcdir/README"`" = "`guix hash /dev/null ; guix hash "$abs_top_srcdir/README"`"
+
+# Zero files.
+! guix hash
+
 ! guix hash -H abcd1234 /dev/null
 
 mkdir "$tmpdir"