* guix/scripts/package.scm (show-help): Add help text for --install-from-file
option.
(%options): Add --install-from-file option.
* tests/guix-package.sh: Test it.
* doc/guix.texi ("invoking guix package"): Document it.
* doc/package-hello.scm: New file.
* doc.am (EXTRA_DIST): Add it.
David Thompson