gnu: Search for patches under $GUIX_PACKAGE_PATH.

Fixes <http://bugs.gnu.org/19364>.
Reported by Tomáš Čech <sleep_walker@suse.cz>
and Mark H Weaver <mhw@netris.org>.

* gnu/packages.scm (%patch-path): Move after definition of
  %package-module-path'.  Append "/gnu/packages/patches" only to
  %DISTRO-ROOT-DIRECTORY.
* tests/guix-package.sh: Add 'emacs-foo-bar-patched' test.

Merge branch 'master' into xorg-updates

packages: Sort Scheme file lists used by 'fold-packages'.

* gnu/packages.scm (scheme-files): Call 'sort' on result.

gnu-maintenance: Introduce <gnu-release> data type.

* guix/gnu-maintenance.scm (<gnu-release>): New record type.
  (release-file): Rename to...
  (release-file?): ... this.  Return a Boolean.
  (tarball->version, coalesce-releases): New procedures.
  (releases): Call 'coalesce-releases' on RESULT.  Return <gnu-release>
  objects instead of pairs.
  (latest-release): Likewise.
  (package-update-path): Adjust accordingly.
* gnu/packages.scm (check-package-freshness): Adjust accordingly.

packages: Optimize 'find-packages-by-name' to avoid disk accesses.

On a profile with 182 entries, "guix package --search-paths" goes from
4.5 seconds down to 0.4 second.

* gnu/packages.scm (find-packages-by-name): Make a name -> package vhash
  in a promise; access it with 'vhash-fold*'.

Introduce the 'GUIX_PACKAGE_PATH' environment variable.

* gnu/packages.scm (%package-module-path): Honor $GUIX_PACKAGE_PATH.
* test-env.in: Unset 'GUIX_PACKAGE_PATH'.
* tests/guix-package.sh: Test it.
* doc/guix.texi (Package Modules): Document it.

packages: Add '%package-module-search-path'.

* gnu/packages.scm (%package-module-path): New variable.
  (all-package-modules): New procedure.
  (fold-packages): Use it instead of 'package-modules'.

packages: Generalize package module search.

* gnu/packages.scm (%distro-root-directory): New variable.
  (%distro-module-directory): Remove.
  (package-files): Rename to...
  (scheme-files): ... this.  Return absolute file names, not stripped.
  (file-name->module-name): New procedure.
  (package-modules): Add 'directory' and 'sub-directory' parameters.
  Rewrite accordingly.
  (fold-packages): Adjust 'package-modules' call accordingly.

Merge branch 'master' into core-updates

Move specification->package to gnu/packages.scm.

* guix/scripts/build.scm (specification->package): Move from here...
* gnu/packages.scm: ... to here.

Merge branch 'master' into core-updates

Move 'check-package-freshness' from 'guix package' to 'packages'.

* guix/scripts/package.scm (%sigint-prompt, call-with-sigint-handler)
  (waiting, ftp-open*, check-package-freshness): Move to...
* gnu/packages.scm: ... here.

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

packages: Remove dead code.

* gnu/packages.scm (_): Remove.
  Remove an extra space.

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

Merge branch 'master' into core-updates

guix: refresh: Add --list-dependent option.

* guix/packages.scm (package-direct-inputs): New procedure.
* gnu/packages.scm (vhash-refq, package-direct-dependents)
  (package-transitive-dependents, package-covering-dependents): New procedures.
* guix/scripts/refresh.scm (%options, show-help, guix-refresh): Add
  --list-dependent option.
* doc/guix.texi (Invoking guix refresh): Document '--list-dependent' option.

Merge branch 'master' into core-updates

Factorize package search between 'guix package' and 'guix build'.

* guix/scripts/package.scm (newest-available-packages): Remove.
  (find-best-packages-by-name): Move to...
* gnu/packages.scm (find-best-packages-by-name): ... here.
  (find-newest-available-packages): Memoize.
* guix/scripts/build.scm (specification->package): New procedure,
  formerly called 'find-package' within 'guix-build'.
  (guix-build): Adjust accordingly.

Merge branch 'master' into core-updates

Conflicts:
	Makefile.am
	gnu/packages/autotools.scm
	gnu/packages/guile.scm
	gnu/packages/python.scm
	gnu/packages/shishi.scm
	guix/gnu-maintenance.scm
	guix/scripts/build.scm
	guix/scripts/gc.scm
	guix/scripts/package.scm
	guix/scripts/substitute-binary.scm
	guix/ui.scm
	nix/nix-daemon/guix-daemon.cc
	test-env.in
	tests/nar.scm
	tests/store.scm

ui: Add a 'define-diagnostic' macro.

* guix/ui.scm (define-diagnostic): New macro, which is based on the
  previous version of 'warning'.
  (warning, leave): Redefine using 'define-diagnostic'.
  (report-error): New macro.
  (install-locale): Use 'warning' instead of 'format'.
  (call-with-error-handling): Adjust 'leave'.
* gnu/packages.scm (package-files): Use 'warning' instead of 'format'.
* guix/gnu-maintenance.scm (http-fetch): Use 'warning' and 'leave'.
* guix/scripts/build.scm (derivations-from-package-expressions, guix-build):
  Adjust 'leave'.
* guix/scripts/download.scm (guix-download): Adjust 'leave'.
* guix/scripts/gc.scm (size->number, %options): Adjust 'leave'.
* guix/scripts/package.scm (roll-back, guix-package): Adjust 'leave'.
* po/POTFILES.in: Add 'guix/gnu-maintenance.scm'.

utils: Add `fold2'.

* gnu/packages.scm (fold2): Remove.
* guix/utils.scm (fold2): New procedure.  Generalization of the above to
  one and two lists.
* tests/utils.scm ("fold2, 1 list", "fold2, 2 lists"): New tests.