guix package: Fix handling of `-e'.

This fixes a bug whereby a command like

  guix package -e '(@@ (gnu packages base) gnu-make-boot0)'

would only succeed when the outputs of that package are available, and
otherwise fail with "/nix/store/... is not valid".

* guix/scripts/package.scm (guix-package)[process-action](package->tuple):
  Leave P as is in the result.  Move `package->tuple' call from INSTALL*
  to INSTALL.

guix package: Reuse FTP connections for subsequent `latest-release' calls.

* guix/gnu-maintenance.scm (latest-release): Add `ftp-close' and
  `ftp-open' keyword parameters.
* guix/scripts/package.scm (ftp-open*): New variable.
  (check-package-freshness): Call `latest-release' with `ftp-open*' and
  a no-op procedure.

Merge branch 'master' into core-updates

Conflicts:
	gnu/packages/make-bootstrap.scm

package: Fix i18n of the number of packages message.

* guix/scripts/package.scm (guix-package)[process-actions]: Use `N_' for
  i18n of the number of packages message.

package: Display the number of installed packages upon completion.

* guix/scripts/package.scm (guix-package)[process-actions]: Display the
  number of packages in the profile upon completion.

build, package: Add `--fallback' option.

* guix/scripts/build.scm (%options, show-help): Add `--fallback'.
  (guix-build): Call `set-build-options' with #:fallback?.
* guix/scripts/package.scm (%options, show-help): Add `--fallback'.
  (guix-package): Call `set-build-options' with #:fallback?.
* doc/guix.texi (Invoking guix package, Invoking guix build): Document
  `--fallback'.

package: Fix default profile ownership check when it's just been created.

* guix/scripts/package.scm (guix-package)[ensure-default-profile]: Check
  whether S is true before checking its owner.  Fixes the case where we
  built %PROFILE-DIRECTORY just above.

Add `--max-silent-time' to `guix build' and `guix package'.

* guix/scripts/build.scm (%default-options): Add default
  `max-silent-time' value.
  (show-help, %options):  Add `--max-silent-time'.
  (guix-build): Pass `max-silent-time' to `set-build-options'.
* guix/scripts/package.scm (%default-options): Add default
  `max-silent-time' value.
  (show-help, %options):  Add `--max-silent-time'.
  (guix-package): Pass `max-silent-time' to `set-build-options'.
* guix/ui.scm (string->number*): New procedure.
* tests/derivations.scm ("build-expression->derivation and
  max-silent-time"): New test.
* doc/guix.texi (Invoking guix package, Invoking guix build): Document
  `--max-silent-time'.

package: Make sure the profile directory is owned by the user.

* guix/scripts/package.scm (guix-package)[ensure-default-profile]: Check
  the owner of %PROFILE-DIRECTORY.  Report an error when the owner is
  not the current user.  Add `rtfm' procedure.
* doc/guix.texi (Invoking guix package): Mention the ownership test.

package: Always clear the SIGINT handler.

* guix/scripts/package.scm (call-with-sigint-handler): Wrap THUNK in
  `dynamic-wind' so that the SIGINT handler is always cleared.

ftp-client: Let callers handle `ftp-open' exceptions.

* guix/ftp-client.scm (ftp-open): Let exceptions through.
* guix/scripts/package.scm (waiting): Wrap EXP in a `dynamic-wind', so
  the line is always cleared.

package: Store the output path of packages installed with `-e'.

* guix/scripts/package.scm (guix-package)[process-actions](package->tuple):
  Put the output path in the tuple, not the derivation path.
* tests/guix-package.sh: Add test.

package: Make sure the dependencies get built along with the manifest.

Before this, something like "guix package -i glibc" could fail because
glibc lists linux-libre-headers as a propagated input (which would be
added as a dependency in the manifest) but the linux-libre-headers
output could be unavailable, leading to an error like this:

  path `/nix/store/4v2bk8sx5cm166gks3fi3q7d9zchibnk-linux-libre-headers-3.3.8' is not valid

This patch adds such dependencies as inputs of the profile derivation.

* guix/scripts/package.scm (profile-derivation): Accept package objects
  in the `deps' field of an element of PACKAGES.  Convert them to their
  output path for BUILDER, and add them to the inputs of the
  `build-expression->derivation' call.
  (input->name+path): When INPUT doesn't contain a package object,
  return it as is.
  (guix-package)[process-actions](canonicalize-deps): Expect DEPS to
  contain package objects, and leave them as is.

package: Use ~/.guix-profile as the default for --search-paths.

* guix/scripts/package.scm (search-path-environment-variables): Prefer
  %USER-ENVIRONMENT-DIRECTORY when it points to PROFILE.
  (display-search-paths): Use 3 spaces for indentation.

package: Display the output of packages to be installed/removed.

* guix/scripts/package.scm (guix-package)[show-what-to-remove/install]:
  Display the output name.

package: Preserve the installed package output when upgrading.

* guix/scripts/package.scm (guix-package)[find-package]: Add optional
  parameter `output'.  Use it.
  [process-actions]: When computing UPGRADE, pass OUTPUT to
  `find-package'.

package: Fix spacing in user messages.

* guix/scripts/package.scm (guix-package)[process-actions]: Fix spacing.

Merge branch 'core-updates'

guix package: Add `--search-paths' & co.

* guix/scripts/package.scm (search-path-environment-variables,
  display-search-paths): New procedures.
  (show-help, %options): Add `--search-paths'.
  (guix-package)[process-actions]: Call `display-search-paths' once the
  profile is ready.
  [process-query]: Honor `search-paths'.

ui: Add `args-fold*' and use it.

* guix/ui.scm (args-fold*): New procedure.
* guix/scripts/build.scm, guix/scripts/download.scm,
  guix/scripts/gc.scm, guix/scripts/hash.scm, guix/scripts/import.scm,
  guix/scripts/package.scm, guix/scripts/pull.scm,
  guix/scripts/refresh.scm: Use `args-fold*' instead of `args-fold'.