Allow user and group patterns to contain . and @, but only groups start with @

Signed-off-by: Robin H. Johnson <robbat2@gentoo.org>
Ensure stdout/stderr/stdin are always restored correctly.

Signed-off-by: Robin H. Johnson <robbat2@gentoo.org>
Instead of mangling stdin and stdout, pass --output for output file with a /dev/fd/X argument and use /dev/fd/X as the file for input. This is important to make the GnuPG agent work better, as gpg disables some pinentry curses functionality if stdin/stdout are overidden.

Signed-off-by: Robin H. Johnson <robbat2@gentoo.org>
Documentation/help cleanup.

Signed-off-by: Robin H. Johnson <robbat2@gentoo.org>