guix package: Register non-default profiles as GC roots.

* guix/scripts/package.scm (maybe-register-gc-root): New procedure.
* tests/guix-package.sh (profile): Grep the output of "guix gc
  --list-live" in a couple of places.

Merge branch 'core-updates'

tests: Adjust to recent Binutils change.

* tests/guix-package.sh: Refer to 'glibc:debug' instead of
  'binutils:lib' since the latter no longer exists.

Merge branch 'master' into core-updates

guix package: Gracefully deal with EPIPE on stdout for --list-*.

* guix/scripts/package.scm (leave-on-EPIPE): New macro.
  (guix-package): Use it for 'list-installed', 'list-available', and
  '--list-generations'.
* tests/guix-package.sh: Add test.

guix package: allow multiple arguments after -i, -r, and -u.

* guix/scripts/package.scm (%options): Adapt option processors to accept and
  return a second seed value: 'arg-handler', which handles bare arguments (if
  not false).  The install, remove, and upgrade option processors return an
  arg-handler that repeat the same operation.  All other option processors
  return #f as the arg-handler.  Make the arguments to install and remove
  optional.  The upgrade option processor deletes (upgrade . #f) from the
  alist before adding a new entry.
  (guix-package): Procedures passed to 'args-fold*' accept the new seed value
  'arg-handler'.  The 'operand-proc' uses 'arg-handler' (if not false).

* doc/guix.texi (Invoking guix package): Update docs.

* tests/guix-package.sh: Add test.

guix package: '--delete-generations' deletes generations older than specified.

* guix/scripts/package.scm (matching-generations): Add
  'duration-relation' keyword parameter.
  (guix-package)[process-action](delete-generations): Pass
  #:duration-relation >.
* tests/guix-package.sh: Add test.
* doc/guix.texi (Invoking guix package): Clarify the meaning of
  durations for '--list-durations' and '--delete-durations'.

tests: Fix typo.

* tests/guix-package.sh: Add missing "-p" option.

guix package: Add '--delete-generations'.

* guix/scripts/package.scm (switch-to-previous-generation): New function.
  (roll-back): Use the new function instead of 'switch-link'.
  (show-help): Add '--delete-generations'.
  (%options): Likewise.
  (guix-package)[process-actions]: Add 'current-generation-number',
  'display-and-delete', and 'delete-generation'.  Add support for
  '--delete-generations', and reindent the code.
* tests/guix-package.sh: Test '--delete-generations'.
* doc/guix.texi (Invoking guix-package): Document '--delete-generations'.

Merge branch 'master' into core-updates

guix package: Show which generation is the current one.

* guix/scripts/package.scm (guix-package)[process-query]: Show that a
  generation is the current one if the profile points to it.
* tests/guix-package.sh: Test it.

tests: Use 'test -z' to check that a string equals zero.

guix package: Do not list the zeroth generation.

* guix/scripts/package.scm (guix-package)[process-query]: Change
  'list-generation' to not list the zeroth generation.
* tests/guix-package.sh: Test it.
* doc/guix.texi (Invoking guix package): Document it, and use the
  right term when talking about generations.

guix package: Exit with 1 when a generation cannot be listed.

* guix/scripts/package.scm (guix-package)[process-query]: Exit with 1
  when a generation does not exist or the profile points to the zeroth
  generation.
* tests/guix-package.sh: Test the former case.

Merge branch 'master' into core-updates

guix package: Add '--list-generations'.

* guix/scripts/package.scm: Import (srfi srfi-19).
  (generation-time, matching-generations): New functions.
  (show-help): Add '--list-generations'.
  (%options): Likewise.
  (guix-package)[process-query]: Add support for '--list-generations'.
* guix/ui.scm: Import (srfi srfi-19) and (ice-9 regex).
  (string->generations, string->duration): New functions.
* tests/guix-package.sh: Test '--list-generations'.
* tests/ui.scm: Import (srfi srfi-19).
  Test 'string->generations' and 'string->duration'.
* doc/guix.texi (Invoking guix-package): Document '--list-generations'.

tests: Clarify filtering of the "debug" output.

* tests/guix-package.sh: Clearly filter out the "debug" output of
  'gnu-make-boot0'.

tests: Fix guix-package.sh in the presence of multiple-output `make'.

* tests/guix-package.sh: For $boot_make_drv, take only the "out" output.
  Reported by Nikita Karetnikov <nikita@karetnikov.org>.

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.

Merge branch 'core-updates'