Merge branch 'master' into core-updates

substitute: Fix file descriptor leak in 'http-multiple-get'.

In practice we would not leak much since we reconnect after ~100
requests (with nginx running on hydra.gnu.org.)

* guix/scripts/substitute.scm (http-multiple-get): Call 'close-port'
  before 'connect'.

guix package: Fix 'readlink*' implementation.

* guix/scripts/package.scm (readlink*): Fix to handle symlinks with
  relative targets.  Taken from ld-wrapper2.in.

guix package: -A and -s take supported systems into account.

* guix/scripts/package.scm (guix-package)[process-query]
  <list-available>: Restrict results to packages matching
  'supported-package?".
* guix/ui.scm (package->recutils): Print "systems:".
* tests/guix-package.sh: Add tests.
* doc/guix.texi (Invoking guix package): Adjust description of
  '--list-available' accordingly.

Merge branch 'core-updates'

Merge branch 'master' into core-updates

Conflicts:
	gnu-system.am
	gnu/packages/gstreamer.scm

refresh: Allow users to refer to specific package versions.

* guix/scripts/refresh.scm (guix-refresh): Use 'specification->package'
  instead of 'find-packages-by-name'.  This allows users to specify
  things like "qt-4.8.6".
* doc/guix.texi (Invoking guix refresh): Add an example.

profiles: Generalize "hooks" for 'profile-derivation'.

* guix/profiles.scm (info-dir-file): Remove (null? (manifest-entries
  manifest)) test.
  (ca-certificate-bundle): Likewise.
  (ghc-package-cache-file): Turn 'if' into 'and', and remove second
  arm.
  (%default-profile-hooks): New variable.
  (profile-derivation): Remove #:info-dir?, #:ghc-package-cache?, and
  #:ca-certificate-bundle?.  Add #:hooks.  Iterate over HOOKS.  Adjust
  'inputs' accordingly.
* guix/scripts/package.scm (guix-package): Adjust 'profile-derivation'
  call accordingly.
* tests/packages.scm ("--search-paths with pattern"): Likewise.
* tests/profiles.scm ("profile-derivation",
  "profile-derivation, inputs"): Likewise.

guix package: Add '--do-not-upgrade' option.

* guix/scripts/package.scm (%options): Add the '--do-not-upgrade' option.
  (show-help): Document it.
  (options->installable): Add 'do-not-upgrade-regexps' variable.
  Use it in 'packages-to-upgrade'.
* doc/guix.texi (Invoking guix package): Document the '--do-not-upgrade'
  option.

lint: Add a 'derivation' checker.

* guix/scripts/lint.scm (check-derivation): New procedure.
  (%checkers): Add 'derivation' checker.
* tests/lint.scm ("derivation: invalid arguments"): New test.

lint: Report patches that cannot be found.

* guix/scripts/lint.scm (check-patch-file-names): Wrap body in 'guard'.
* tests/lint.scm ("patches: not found"): New test.

lint: Rename 'check-patches' to 'check-patch-file-names'.

* guix/scripts/lint.scm (check-patches): Rename to...
  (check-patch-file-names): ... this.  Rename 'filename' to 'file'.
  (%checkers): Adjust accordingly.
* tests/lint.scm ("patches: file names"): Likewise.

Merge branch 'master' into core-updates

profiles: Generate GHC's package database cache.

* guix/profiles.scm (ghc-package-cache-file): New procedure.
  (profile-derivation): Add 'ghc-package-cache?' keyword argument.  If true
  (the default), add the result of 'ghc-package-cache-file' to 'inputs'.
* guix/scripts/package.scm (guix-package)[process-actions]: Pass
  #:ghc-package-cache? to 'profile-generation'.
* tests/packages.scm ("--search-paths with pattern"): Likewise.
* tests/profiles.scm ("profile-derivation"): Likewise.

import: Add hackage importer.

* guix/scripts/import.scm (importers): Add hackage.
* guix/scripts/import/hackage.scm: New file.
* po/guix/POTFILES.in: Add guix/scripts/import.scm.
* doc/guix.texi: Add section on 'hackage' importer.

Merge branch 'master' into core-updates

ui: Add 'report-load-error'.

* guix/scripts/system.scm (read-operating-system): Replace error
  handling code by a call to 'report-load-error'.
* guix/ui.scm (report-load-error): New procedure.

guix package: Avoid 'exit' calls in 'delete-matching-generations'.

* guix/scripts/package.scm (delete-matching-generations): Remove call to
  'exit' when PATTERN is "0".  Call 'leave' instead of 'exit'
  when (null-list? number).

guix package: Never remove the current generation and warn about it.

Fixes <http://bugs.gnu.org/19978>.
Reported by taylanbayirli@gmail.com (Taylan Ulrich Bayırlı/Kammer).

* guix/scripts/package.scm (delete-matching-generations): Warn when
  CURRENT is in NUMBERS, and always remove it before calling
  'delete-generations'.
* tests/guix-package.sh: Add --switch-generation=2 invocation before
  --delete-generations=3 invocation.
  Add --delete-generations=1.. test case.

guix package: Move generation deletion to its own procedure.

* guix/scripts/package.scm (delete-matching-generations): New procedure,
  with code formerly found...
  (guix-package)[process-actions]: ... here.  Use it.
  Remove 'current-generation-number'.