guix hash: Add '--recursive'.

* guix/scripts/hash.scm (show-help): Add --recursive.
  (%options): Likewise.
  (guix-hash)[file-hash]: New procedure.  Honor --recursive.
  Use it.
* guix/nar.scm (write-file): Add missing field to the &nar-error
  condition raised upon unsupported file type; change its message to be
  more descriptive.
* tests/guix-hash.sh: Add tests with -r.
* doc/guix.texi (Invoking guix hash): Document --recursive.

doc/guix.texi

@@ -1958,6 +1958,19 @@ If the @option{--format} option is not specified, @command{guix hash}
 will output the hash in @code{nix-base32}.  This representation is used
 in the definitions of packages.
 
+@item --recursive
+@itemx -r
+Compute the hash on @var{file} recursively.
+
+In this case, the hash is computed on an archive containing @var{file},
+including its children if it is a directory.  Some of @var{file}'s
+meta-data is part of the archive; for instance, when @var{file} is a
+regular file, the hash is different depending on whether @var{file} is
+executable or not.  Meta-data such as time stamps has no impact on the
+hash (@pxref{Invoking guix archive}).
+@c FIXME: Replace xref above with xref to an ``Archive'' section when
+@c it exists.
+
 @end table
 
 @node Invoking guix refresh

guix/nar.scm

@@ -195,8 +195,8 @@ sub-directories of FILE as needed."
          (write-string "target" p)
          (write-string (readlink f) p))
         (else
-         (raise (condition (&message (message "ENOSYS"))
-                           (&nar-error)))))
+         (raise (condition (&message (message "unsupported file type"))
+                           (&nar-error (file f) (port port))))))
       (write-string ")" p))))
 
 (define (restore-file port file)

guix/scripts/hash.scm

@@ -20,12 +20,14 @@
 (define-module (guix scripts hash)
   #:use-module (guix base32)
   #:use-module (guix hash)
+  #:use-module (guix nar)
   #:use-module (guix ui)
   #:use-module (guix utils)
   #:use-module (rnrs io ports)
   #:use-module (rnrs files)
   #:use-module (ice-9 match)
   #:use-module (srfi srfi-1)
+  #:use-module (srfi srfi-11)
   #:use-module (srfi srfi-26)
   #:use-module (srfi srfi-37)
   #:export (guix-hash))
@@ -43,10 +45,12 @@
   (display (_ "Usage: guix hash [OPTION] FILE
 Return the cryptographic hash of FILE.
 
-Supported formats: 'nix-base32' (default), 'base32', and 'base16'
-('hex' and 'hexadecimal' can be used as well).\n"))
+Supported formats: 'nix-base32' (default), 'base32', and 'base16' ('hex'
+and 'hexadecimal' can be used as well).\n"))
   (format #t (_ "
   -f, --format=FMT       write the hash in the given format"))
+  (format #t (_ "
+  -r, --recursive        compute the hash on FILE recursively"))
   (newline)
   (display (_ "
   -h, --help             display this help and exit"))
@@ -73,6 +77,9 @@ Supported formats: 'nix-base32' (default), 'base32', and 'base16'
 
                   (alist-cons 'format fmt-proc
                               (alist-delete 'format result))))
+        (option '(#\r "recursive") #f #f
+                (lambda (opt name arg result)
+                  (alist-cons 'recursive? #t result)))
 
         (option '(#\h "help") #f #f
                 (lambda args
@@ -107,12 +114,22 @@ Supported formats: 'nix-base32' (default), 'base32', and 'base16'
                            (reverse opts)))
          (fmt  (assq-ref opts 'format)))
 
+    (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?)
+            (let-values (((port get-hash) (open-sha256-port)))
+              (write-file file port)
+              (flush-output-port port)
+              (get-hash))
+            (call-with-input-file file port-sha256))))
+
     (match args
       ((file)
        (catch 'system-error
          (lambda ()
-           (format #t "~a~%"
-                   (fmt (call-with-input-file file port-sha256))))
+           (format #t "~a~%" (fmt (file-hash file))))
          (lambda args
            (leave (_ "~a~%")
                   (strerror (system-error-errno args))))))

tests/guix-hash.sh

@@ -1,5 +1,5 @@
 # GNU Guix --- Functional package management for GNU
-# Copyright © 2013 Ludovic Courtès <ludo@gnu.org>
+# Copyright © 2013, 2014 Ludovic Courtès <ludo@gnu.org>
 #
 # This file is part of GNU Guix.
 #
@@ -22,7 +22,27 @@
 
 guix hash --version
 
+tmpdir="guix-hash-$$"
+trap 'rm -rf "$tmpdir"' EXIT
+
 test `guix hash /dev/null` = 0mdqa9w1p6cmli6976v4wi0sw9r4p5prkj7lzfd1877wk11c9c73
 test `guix hash -f nix-base32 /dev/null` = 0mdqa9w1p6cmli6976v4wi0sw9r4p5prkj7lzfd1877wk11c9c73
 test `guix hash -f hex /dev/null` = e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855
 test `guix hash -f base32 /dev/null` = 4oymiquy7qobjgx36tejs35zeqt24qpemsnzgtfeswmrw6csxbkq
+
+mkdir "$tmpdir"
+echo -n executable > "$tmpdir/exe"
+chmod +x "$tmpdir/exe"
+( cd "$tmpdir" ; ln -s exe symlink )
+mkdir "$tmpdir/subdir"
+
+test `guix hash -r "$tmpdir"` = 10k1lw41wyrjf9mxydi0is5nkpynlsvgslinics4ppir13g7d74p
+
+# Without '-r', this should fail.
+if guix hash "$tmpdir"
+then false; else true; fi
+
+# This should fail because /dev/null is a character device, which
+# the archive format doesn't support.
+if guix hash -r /dev/null
+then false; else true; fi