gnu: Add duplicity.

* gnu/packages/backup.scm: New file.
* gnu-system.am: Add it.

gnu-system.am

@@ -36,6 +36,7 @@ GNU_SYSTEM_MODULES =				\
   gnu/packages/autogen.scm			\
   gnu/packages/autotools.scm			\
   gnu/packages/avahi.scm			\
+  gnu/packages/backup.scm			\
   gnu/packages/base.scm				\
   gnu/packages/bash.scm				\
   gnu/packages/bdb.scm				\

gnu/packages/backup.scm

@@ -0,0 +1,71 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2014 Eric Bavier <bavier@member.fsf.org>
+;;;
+;;; This file is part of GNU Guix.
+;;;
+;;; GNU Guix is free software; you can redistribute it and/or modify it
+;;; under the terms of the GNU General Public License as published by
+;;; the Free Software Foundation; either version 3 of the License, or (at
+;;; your option) any later version.
+;;;
+;;; GNU Guix is distributed in the hope that it will be useful, but
+;;; WITHOUT ANY WARRANTY; without even the implied warranty of
+;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;;; GNU General Public License for more details.
+;;;
+;;; You should have received a copy of the GNU General Public License
+;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
+
+(define-module (gnu packages backup)
+  #:use-module (guix packages)
+  #:use-module (guix licenses)
+  #:use-module (guix download)
+  #:use-module (guix build-system python)
+  #:use-module (gnu packages)
+  #:use-module (gnu packages python)
+  #:use-module (gnu packages gnupg)
+  #:use-module (gnu packages rsync)
+  #:use-module (srfi srfi-1))
+
+(define-public duplicity
+  (package
+    (name "duplicity")
+    (version "0.6.24")
+    (source
+     (origin
+      (method url-fetch)
+      (uri (string-append "https://code.launchpad.net/duplicity/"
+                          (string-join (take (string-split version #\.) 2) ".")
+                          "-series/" version "/+download/duplicity-"
+                          version ".tar.gz"))
+      (sha256
+       (base32
+        "0l14nrhbgkyjgvh339bbhnm6hrdwrjadphq1jmpi0mcgcdbdfh8x"))))
+    (build-system python-build-system)
+    (native-inputs
+     `(("python2-setuptools" ,python2-setuptools)))
+    (inputs
+     `(("python" ,python-2)
+       ("librsync" ,librsync)
+       ("mock" ,python2-mock)           ;for testing
+       ("lockfile" ,python2-lockfile)
+       ("gnupg" ,gnupg-1)))             ;gpg executable needed
+    (arguments
+     `(#:python ,python-2               ;setup assumes Python 2
+       #:test-target "test"
+       #:phases (alist-cons-before
+                 'check 'patch-tests
+                 (lambda _
+                   (substitute* "testing/functional/__init__.py"
+                     (("/bin/sh") (which "sh"))))
+                 %standard-phases)))
+    (home-page "http://duplicity.nongnu.org/index.html")
+    (synopsis "Encrypted backup using rsync algorithm")
+    (description
+     "Duplicity backs up directories by producing encrypted tar-format volumes
+and uploading them to a remote or local file server.  Because duplicity uses
+librsync, the incremental archives are space efficient and only record the
+parts of files that have changed since the last backup.  Because duplicity
+uses GnuPG to encrypt and/or sign these archives, they will be safe from
+spying and/or modification by the server.")
+    (license gpl2+)))