import: Add Ruby gem importer.

* gnu/scripts/import.scm (importers): Add "gem".
* gnu/import/gem.scm: New file.
* gnu/scripts/import/gem.scm: New file.
* Makefile.am (MODULES): Add them.
* guix.texi ("invoking guix import"): Document it.

import: pypi: Move generally useful procedures to utils module.

* guix/import/pypi.scm (make-pypi-sexp): Factorize license to symbol
  conversion code.
  (string->license, snake-case, guix-hash-url): Move from here...
* guix/import/utils.scm: ... to here.
  (license->symbol): New procedure.

gnu: Add ruby-arel.

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

gnu: Add conky.

* gnu/packages/conky.scm: New file.
* gnu-system.am (GNU_SYSTEM_MODULES): Add it.

Co-authored-by: Ludovic Courtès <ludo@gnu.org>

gnu: lua: Add patch to generate pkg-config file.

* gnu/packages/patches/lua-pkgconfig.patch: New file.
* gnu/packages/lua.scm (lua)[source]: Add patch.
* gnu-system.am (dist_patch_DATA): Register patch.

Signed-off-by: Ludovic Courtès <ludo@gnu.org>

Thank Eric Hanchrow.

emacs: Add completions for 'guix graph'.

* emacs/guix-pcomplete.el (guix-pcomplete-parse-linter-regexp): Improve
  and rename to ...
  (guix-pcomplete-parse-list-regexp): ...this.  New variable.
  (guix-pcomplete-lint-checkers): Use it.
  (guix-pcomplete-graph-types): New function.
  (guix-pcomplete-complete-command-arg): Complete package names for
  'guix graph' command.
  (guix-pcomplete-complete-option-arg): Complete '-t/--type' option.

gnu: git-modes: Update to 1.2.0.

* gnu/packages/emacs.scm (git-modes): Update to 1.2.0.
  [arguments]: Disable tests.

gnu: magit-svn: Update to 2.1.0.

* gnu/packages/emacs.scm: Use (gnu packages base) module.  Remove
  duplicated (gnu packages guile) and (gnu packages linux) modules.
  (magit-svn): Update to 2.1.0.
  [source]: Use 'url-fetch' method.
  [inputs]: Remove.  Move "emacs" to 'native-inputs', move "magit" to
  'propagated-inputs'.
  [native-inputs]: Add "tar" and "gzip".
  [propagated-inputs]: Add "dash".
  [arguments]: Adjust builder for the new inputs and unpacking the source.

gnu: magit: Update to 2.2.1.

* gnu/packages/emacs.scm (magit): Update to 2.2.1.
  [inputs]: Remove 'git:gui'.
  [propagated-inputs]: Add 'dash', remove 'git-modes'.
  [arguments]: Add PREFIX and DASH_DIR to 'make-flags'.  Remove
  'configure', 'augment-load-path' and 'post-install' phases.

daemon: Require a signature for imports made by root.

This reinstates commit aa0f8409, which was inadvertently undone in commit
322eeb87.

Running 'guix archive --import' as root would have let corrupt or unauthentic
store items through.

Reported by Eric Hanchrow <eric.hanchrow@gmail.com>
at <http://bugs.gnu.org/21354>.

* nix/nix-daemon/nix-daemon.cc (performOp) <wopImportPaths>: Pass true as the
  first argument to 'importPaths'.

tests: Skip 'set-network-interface-address' test when running as root.

Reported by Eric Hanchrow <eric.hanchrow@gmail.com>
in <http://bugs.gnu.org/21354>.

* tests/syscalls.scm ("set-network-interface-address"): Skip when (getuid)
  returns zero.

Add graph.scm to 'POTFILES'.

* po/guix/POTFILES.in: Add guix/scripts/graph.scm.

Add 'guix graph'.

* guix/scripts/graph.scm, tests/graph.scm, tests/guix-graph.sh,
  doc/images/coreutils-bag-graph.dot, doc/images/coreutils-graph.dot: New
  files.
* Makefile.am (MODULES): Add guix/scripts/graph.scm.
  (SH_TESTS): Add tests/guix-graph.sh.
  (SCM_TESTS): Add tests/graph.scm.
* doc.am (DOT_FILES, DOT_VECTOR_GRAPHICS): New variables.
  (EXTRA_DIST): Use them.
  (dist_infoimage_DATA): Use $(DOT_FILES).
  (pdf-local, info-local, ps-local): Likewise.
* doc/guix.texi (Packages with Multiple Outputs): Add cross-reference to 'guix
  graph'.
  (Invoking guix gc): Likewise.
  (Invoking guix graph): New section.

build: Do not build (guix build syscalls) if 'mount' is missing from libc.

This disables compilation of this module on GNU/Hurd.
Reported by Manolis Ragkousis <manolis837@gmail.com>.

* m4/guix.m4 (GUIX_CHECK_LIBC_MOUNT): New variable.
* configure.ac: Use it.  Define 'BUILD_SYSCALLS_MODULE' conditional.
* Makefile.am (MODULES, EXTRA_DIST): Make 'guix/build/syscalls.scm'
  conditional on BUILD_SYSCALLS_MODULE.

gexp: Add 'lower-object'.

* guix/gexp.scm (lower-object): New procedure.
  (lower-inputs, lower-references, gexp->sexp): Use it.
* tests/gexp.scm ("lower-object"): New test.
* doc/guix.texi (G-Expressions): Document it.

gnu: Add BioPerl.

* gnu/packages/bioinformatics.scm (bioperl-minimal): New variable.

gnu: pius: Adjust to the new libpius.

Prior to this commit the libpius modules would not be found and the default
GnuPG file name would be /usr/bin/gpg.

* gnu/packages/gnupg.scm (pius)[inputs]: Remove PYTHON-2.
  [build-system]: Switch to PYTHON-BUILD-SYSTEM.
  [arguments]: Add #:python.  Change to add a single phase,
  'set-gpg-file-name'.

tests: Work around Btrfs handling of nlink for empty directories.

Fixes <http://bugs.gnu.org/21280>.
Reported by Leo Famulari <leo@famulari.name>.

* tests/nar.scm (file-tree-equal?): Use #t as the initial result.  Btrfs would
  set nlink to 1 instead of 2 for an empty directory, thereby leading
  'file-tree-equal?' to return #f.

gnu: ratpoison: Clean definition.

* gnu/packages/ratpoison.scm (ratpoison)[arguments]: Use modify-phases.
  [inputs]: Sort alphabetically.  Move ratpoison.desktop to ...
  [native-inputs]: ... here.