* 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.