Fixes <http://bugs.gnu.org/21958>.
* guix/scripts/environment.scm (status->exit-code): New procedure.
(exit/status, primitive-exit/status): Use it.
* tests/guix-environment-container.sh: Add test.
Fixes <http://bugs.gnu.org/21410>.
Reported by Alex Vong <alexvong1995@gmail.com>.
* tests/guix-environment-container.sh: Exit with 77 when
'((@@ (guix scripts environment) assert-container-features))' fails.
* guix/scripts/system.scm (specification->file-system-mapping): Move from
here...
* guix/ui.scm (specification->file-system-mapping): ... to here.
* guix/scripts/enviroment.scm (show-help): Show help for new options.
(%options): Add --container --network, --expose, and --share options.
(%network-configuration-files): New variable.
(launch-environment, launch-environment/container, requisites*,
inputs->requisites): New procedures.
(guix-environment): Spawn new process in a container when requested.
* doc/guix.texi (Invoking guix environment): Document it.
* tests/guix-environment-container.sh: New file.
* Makefile.am (SH_TESTS): Add it.
