gnu: units: Update to 2.12. * gnu/packages/maths.scm (units): Update to 2.12.
Add 'guix challenge'. * 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.
substitute: Expose narinfo access. * guix/scripts/substitute.scm: Export <narinfo> accessors. (narinfo-hash->sha256): New procedure. (cache-narinfo!): Ignore EACCES exceptions.
guix archive: Add '--extract'. * 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: elogind: Provide the file name of 'halt' and 'reboot'. * gnu/packages/freedesktop.scm (elogind)[inputs]: Add DMD.
gnu: gnurl: Update to 7.44.0. * gnu/packages/gnunet.scm (gnurl): Update to 7.44.0.
gnu: calibre: Update to 2.41.0. * gnu/packages/ebook.scm (calibre): Update to 2.41.0.
gnu: youtube-dl: Update to 2015.10.16. * gnu/packages/video.scm (youtube-dl): Update to 2015.10.16.
gnu: ngs-sdk: Correct typo. * gnu/packages/bioinformatics.scm (ngs-sdk): Correct typo.
gnu: ngs-sdk: Remove unsupported systems. * gnu/packages/bioinformatics.scm (ngs-sdk)[supported-systems]: Keep only x86 based systems.
gnu: chess: Update to 6.2.2. * gnu/packages/games.scm (chess): Update to 6.2.2.
gnu: non-sequencer: Disable SSE when not building on x86_64. * gnu/packages/music.scm (non-sequencer)[arguments]: Add "--disable-sse" flag when not building on x86_64.
gnu: fastcap: Remove non-free file. * gnu/packages/engineering.scm (fastcap): Do it.
gnu: fastcap: Fix 'fix-doc phase. * gnu/packages/engineering.scm (fastcap): Adapt documentation generation to change in TeXLive 2015.
emacs: devel: Highlight Guix keywords. * emacs/guix-devel.el (guix-devel-keywords): New constant. (guix-devel-font-lock-keywords): Use it.
doc: emacs: Document "View graph" popup action. * doc/emacs.texi (Emacs Popup Interface): Document "View graph" action.
emacs: Improve file names of generated graphs. 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.
gnu-maintenance: Fix file descriptor leak. * guix/gnu-maintenance.scm (official-gnu-packages): Close the port returned by FETCH.
gnu-maintenance: Use 'http-fetch/cached' by default. 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'.
http-client: Add 'http-fetch/cached'. * guix/utils.scm (cache-directory): New procedure. * guix/http-client.scm (%http-cache-ttl): New variable. (http-fetch/cached): New procedure.