store: Invalidate caches once GC has run.

* guix/store.scm (run-gc): Add calls to 'hash-clear!'.
* tests/store.scm ("add-text-to-store vs. delete-paths",
  "add-to-store vs. delete-paths"): New tests.

Break module cycle involving (guix store) and (guix ui).

Before, there was a cycle along the lines of:

  (guix store) -> (guix nar) -> (guix ui) -> (guix store)

This caused problems, as discussed at:

  http://lists.gnu.org/archive/html/guix-devel/2014-10/msg00109.html

This patch removes cycles in the (guix ...) modules.

* guix/nar.scm (&nar-error, &nar-read-error, dump, write-contents,
  read-contents, %archive-version-1, write-file, restore-file): Move to...
* guix/serialization.scm: ... here.
* guix/store.scm: Remove dependency on (guix nar).
* guix/scripts/hash.scm, guix/scripts/offload.scm,
  guix/scripts/substitute-binary.scm, tests/nar.scm, tests/store.scm,
  tests/substitute-binary.scm: Adjust accordingly.

Merge branch 'master' into core-updates

Factorize test suite support in (guix tests).

* guix/tests.scm: New file.
* Makefile.am (noinst_DATA): New variable.
  (GOBJECTS): Add guix/tests.go.
* tests/builders.scm (%store): Use 'open-connection-for-tests'
  from (guix tests).
* tests/derivations.scm: Likewise.
* tests/monads.scm: Likewise.
* tests/packages.scm: Likewise.
* tests/profiles.scm: Likewise.
* tests/union.scm: Likewise.
* tests/gexp.scm: Likewise.
  (guile-for-build): Remove.  Use (%guile-for-build) instead.
* tests/nar.scm (make-random-bytevector, %seed, random-text): Remove.
  (populate-file): Change 'make-random-bytevector' to 'random-bytevector'.
  Use (guix tests).
* tests/store.scm (%seed, random-text): Remove.
  Use (guix tests).

Merge branch 'master' into core-updates

store: (direct-store-path? (%store-prefix)) returns #f.

* guix/store.scm (direct-store-path?): Return #f if PATH
  is (%store-prefix).
* tests/store.scm ("direct-store-path?"): Add test.

store: Add 'add-permanent-root' and 'remove-permanent-root'.

* guix/store.scm (add-indirect-root): Improve docstring.
  (%gc-roots-directory): New variable.
  (add-permanent-root, remove-permanent-root): New procedures.
* tests/store.scm ("permanent root"): New test.

tests: Make sure the daemon reports substitute hash mismatches.

* tests/store.scm ("substitute, corrupt output hash"): New test.

Merge branch 'master' into core-updates

tests: Test recovery from 'valid-path?' RPCs with an invalid parameter.

* tests/store.scm ("valid-path? live", "valid-path? false", "valid-path?
  error", "valid-path? recovery"): New tests.

Merge branch 'master' into core-updates

store: Add 'hash-part->path'.

* guix/store.scm (hash-part->path): New procedure.
* tests/store.scm ("hash-part->path"): New test.

Merge branch 'master' into core-updates

tests: 'topologically-sorted' test handles different references orders.

* tests/store.scm ("topologically-sorted, more difficult"): Arrange to
  handle a different ordering of (references %store y).

store: 'export-paths' doesn't export references of the given files.

This fixes a regression introduced in
99fbddf9a623757e39d88bfb431f8f7d6f24b75b ("store: Change 'export-paths'
to always export in topological order.")

* guix/store.scm (export-paths): Define 'ordered' variable.  Iterate
  over it.
* tests/store.scm ("export/import paths, ensure topological order"): Add
  'file0'.  Adjust accordingly.

Merge branch 'master' into core-updates

Conflicts:
	gnu-system.am

store: Change 'export-paths' to always export in topological order.

* guix/store.scm (export-paths): Pass PATHS through
  'topologically-sorted' before iterating.
* tests/store.scm ("export/import paths, ensure topological order"): New
  test.

Merge branch 'master' into core-updates

store: Add 'topologically-sorted'.

* guix/store.scm (topologically-sorted): New procedure.
* tests/store.scm ("topologically-sorted, one item",
  "topologically-sorted, several items", "topologically-sorted, more
  difficult"): New tests.

store: Add 'register-path' procedure.

* guix/store.scm (register-path): New procedure.
* tests/store.scm ("register-path"): New test.
* guix/config.scm.in (%guix-register-program): New variable.
* configure.ac: Compute and substitute 'guix_sbindir'.  Compute
  'guix_prefix'.
* pre-inst-env.in: Define 'GUIX_REGISTER'.