snix: Gracefully handle `null' in Nix build inputs.

* guix/snix.scm (snix-derivation->guix-package)[convert-inputs]:
  Gracefully handle `null' as an input.

distro: Add GNU Aspell.

* distro/packages/aspell.scm: New file.
* Makefile.am (MODULES): Add it.

distro: Add GSL.

* distro/packages/algebra.scm (gsl): New variable.

distro: Add GNU GLOBAL.

* distro/packages/global.scm: New file.
* Makefile.am (MODULES): Add it.

distro: Add Tcl, Expect, and DejaGNU.

* distro/packages/dejagnu.scm, distro/packages/tcl.scm: New files.
* Makefile.am (MODULES): Add them.

Update license headers.

Change all license headers, except guix/build/* and ld-wrapper.scm, with
this code:

  (use-modules (guix build utils)
	       (srfi srfi-1))

  (fluid-set! %default-port-encoding "UTF-8")

  (substitute* (remove (lambda (f)
			 (or (string-contains f ".tar.")
			     (string-contains f ".git/")
			     (string-contains f ".so")
			     (string-suffix? ".o" f)
			     (string-suffix? ".a" f)
			     (string-suffix? ".go" f)
			     (string-suffix? ".pdf" f)
			     (string-suffix? ".png" f)
			     (string-suffix? ".info" f)
			     (equal? (basename f) "guix-daemon")
			     (equal? (basename f) "nix-setuid-helper")
			     (string-contains f "nix-upstream/")
			     (string-contains f "distro/packages/bootstrap/")))
		       (find-files "." "\\.[a-z]+$"))
    (("^([[:graph:]]+) This file is part of Guix." _ comment-start)
     (string-append comment-start " This file is part of GNU Guix."))
    (("^([[:graph:]]+) Guix --- Nix package management.*" _ comment-start)
     (string-append comment-start
		    " GNU Guix --- Functional package management for GNU\n"))
    (("^([[:graph:]]+) Guix is " _ comment-start)
     (string-append comment-start " GNU Guix is "))
    (("^([[:graph:]]+) along with Guix." _ comment-start)
     (string-append comment-start " along with GNU Guix."))
    (("^([[:graph:]]+) Copyright \\(C\\)" _ comment-start)
     (string-append comment-start " Copyright ©")))

Change headers using C-style comments manually.

Add `guix-gc'.

* guix-gc.in, tests/guix-gc.sh: New files.
* configure.ac: Output `guix-gc', and make it executable.
* Makefile.am (bin_SCRIPTS): Add `guix-gc'.
  (TESTS): Add `tests/guix-gc.sh'.
* doc/guix.texi (Features): Add xref to "Invoking guix-gc".
  (Invoking guix-gc): New node.
* po/POTFILES.in: Add `guix-gc.in'.

guix-build: Make `--root' effective for .drv files too.

* guix-build.in (guix-build)[register-root]: Change first argument to
  `paths', which should be a list of store paths.  Update caller to call
  `derivation-path->output-paths' on DRV.  When `derivations-only?',
  also register root for .drv files.

derivations: Add `derivation-path->output-paths'.

* guix/derivations.scm (derivation-path->output-paths): New procedure.
* tests/derivations.scm ("multiple-output derivation"): Test it.

ui: Factorize bug-report information in `--help'.

* guix/config.scm.in (%guix-home-page-url): New variable.
* guix/ui.scm (show-bug-report-information): New procedure.
* guix-build.in (show-help): Use it.
* guix-download.in (show-help): Likewise.
* guix-import.in (show-help): Likewise.
* guix-package.in (show-help): Likewise.

daemon: Show the chroot contents upon `--debug'.

* nix/nix-daemon/guix-daemon.cc (main)[HAVE_CHROOT]: Display the
  contents of `settings.dirsInChroot' at `lvlDebug'.

distro: Add Berkeley DB.

* distro/packages/bdb.scm: New file.
* Makefile.am (MODULES): Add it.

distro: Add MIT Kerberos 5.

* distro/packages/mit-krb5.scm: New file.
* Makefile.am (MODULES): Add it.

daemon: Properly initialize libgcrypt.

* nix/nix-daemon/guix-daemon.cc (main): Call `gcry_check_version'.

build: Avoid error message during `make clean' when `test-tmp' doesn't exist.

* daemon.am (clean-local): Check whether $(GUIX_TEST_ROOT) exists before
  running `find'.

distro: Add Libntlm, GNU GSS and GNU SASL.

* distro/packages/gsasl.scm: New file.
* Makefile.am (MODULES): Add it.

distro: automake: Update to 1.12.6.

* distro/packages/autotools.scm (automake): Update to 1.12.6.

distro: Add GNU Libidn.

* distro/packages/libidn.scm: New file.
* Makefile.am (MODULES): Add it.

distro: Update libtasn1 and gnutls.

* distro/packages/gnutls.scm: Update libtasn1 and gnutls.

distro: Add GNU idutils.

* distro/packages/idutils.scm: New file.
* Makefile.am (MODULES): Add it.