Suggested by Ludovic Courtès <ludo@gnu.org>.

* configure.ac: Set DOT_USER_PROGRAM variable.
* emacs/guix-config.el.in (guix-config-dot-program): New constant.
* emacs/guix-external.el (guix-dot-program): Use it.

* gnu/packages/maths.scm (units): Update to 2.12.

* guix/scripts/challenge.scm, tests/challenge.scm: New files.
* Makefile.am (MODULES): Add the former.
  (SCM_TESTS): Add the latter.
* doc.am (SUBCOMMANDS): Add 'challenge'.
* doc/guix.texi (Substitutes): Add xref to 'guix challenge'.
  (Invoking guix challenge): New node.
* doc/contributing.texi (Submitting Patches): Add note about using 'guix
  challenge'.
* po/guix/POTFILES.in: Add guix/scripts/challenge.scm.

* guix/scripts/substitute.scm: Export <narinfo> accessors.
  (narinfo-hash->sha256): New procedure.
  (cache-narinfo!): Ignore EACCES exceptions.

* guix/scripts/archive.scm (show-help, %options): Add --extract.
  (guix-archive): Honor it.
* tests/guix-archive.sh: Test it.
* doc/guix.texi (Invoking guix archive): Document it.

* gnu/packages/freedesktop.scm (elogind)[inputs]: Add DMD.

* gnu/packages/gnunet.scm (gnurl): Update to 7.44.0.

* gnu/packages/ebook.scm (calibre): Update to 2.41.0.

* gnu/packages/video.scm (youtube-dl): Update to 2015.10.16.

* gnu/packages/bioinformatics.scm (ngs-sdk): Correct typo.

* gnu/packages/bioinformatics.scm (ngs-sdk)[supported-systems]: Keep only x86
  based systems.

* gnu/packages/games.scm (chess): Update to 6.2.2.

* gnu/packages/music.scm (non-sequencer)[arguments]: Add "--disable-sse"
  flag when not building on x86_64.

* gnu/packages/engineering.scm (fastcap): Do it.

* gnu/packages/engineering.scm (fastcap): Adapt documentation generation to
  change in TeXLive 2015.

* emacs/guix-devel.el (guix-devel-keywords): New constant.
  (guix-devel-font-lock-keywords): Use it.

* doc/emacs.texi (Emacs Popup Interface): Document "View graph" action.

Suggested by Ludovic Courtès <ludo@gnu.org>.

* emacs/guix-external.el (guix-png-file-name): Change prefix of a file
  name to "guix-emacs-graph-" to avoid possible conflicts.

* guix/gnu-maintenance.scm (official-gnu-packages): Close the port
  returned by FETCH.

This speeds up operations like 'guix lint -c gnu-description'.

* guix/gnu-maintenance.scm (official-gnu-packages): Add 'fetch'
  parameter and honor it.  Default to 'http-fetch/cached'.

* guix/utils.scm (cache-directory): New procedure.
* guix/http-client.scm (%http-cache-ttl): New variable.
  (http-fetch/cached): New procedure.

Reported by anthk_ on #guix in Sept. 2015.

* gnu/system/install.scm (self-contained-tarball): Use --mtime=@1
  instead of --mtime=@0.

* gnu/packages/code.scm (complexity): Update to 1.3.

Reported by David Thompson <dthompson2@worcester.edu>
at <https://lists.gnu.org/archive/html/guix-devel/2015-10/msg00284.html>.

* gnu/build/file-systems.scm (mount-file-system): When SOURCE matches
  'regular-file?', do not create MOUNT-POINT if it already exists.  This
  fixes a bug whereby we would be truncating MOUNT-POINT if it already
  existed.

Fixes <http://bugs.gnu.org/21694>.

* guix/build/syscalls.scm (clone): Change 'syscall' parameter types to
  LONG, UNSIGNED-LONG, or '*; make sure it has 6 parameters.  Adjust
  caller accordingly.

* gnu/packages/patches/mutt-CVE-2014-9116.patch: Delete file.
* gnu/packages/mail.scm (mutt): Update to 1.5.24.
  [source]: Update and remove patch.
* gnu-system.am (dist_patch_DATA): Unregister removed patch.

* gnu/packages/wm.scm (bspwm): New variable.

Signed-off-by: Alex Kost <alezost@gmail.com>

* gnu/packages/xdisorg.scm (sxhkd): New variable.

Signed-off-by: Alex Kost <alezost@gmail.com>

* emacs/guix-command.el (guix-command-additional-execute-arguments,
  guix-command-special-executors): Add "View graph" actions for
  'dmd-graph' and 'extension-graph' commands.

* emacs/guix-command.el (guix-command-improve-system-argument): Use "D"
  key for 'disk-image' action (leave "d" for 'dmd-graph').

Fixes a regression introduced in 77411390.

Reported by Ludovic Courtès <ludo@gnu.org>.

Not all emacs packages have "...-autoloads.el" files, so there is a
chance that "~/.guix-profile/share/emacs/site-lisp" will not be added to
'load-path', so add it unconditionally.

* emacs/guix-init.el: Add guix emacs directory to 'load-path'.  Move
  requiring 'guix-emacs' to the top-level.

* gnu/system.scm (operating-system-etc-service)[profile]: Add
  'GST_PLUGIN_PATH' definition.

* doc/images/coreutils-bag-graph.dot, doc/images/coreutils-graph.dot:
  Regenerate from current packages.  This removes the weird dependency
  on 'sed'.

* gnu/packages/python.scm (python-libarchive-c, python2-libarchive-c):
  New variables.

* gnu/packages/python.scm (python-tlsh, python2-tlsh): New variable.

* gnu/packages/ruby.scm (ruby-yard): New variable.

* gnu/packages/ruby.scm (ruby-rspec-2): New variable.

* gnu/packages/ruby.scm (ruby-rspec-mocks-2): New variable.

* gnu/packages/ruby.scm (ruby-rspec-expectations-2): New variable.

* gnu/packages/ruby.scm (ruby-rspec-core-2): New variable.