ejabberdctl: support OpenBSD su

[catap]

OpenBSD has a different than Linux su:

1. -c before username is treated as login class;
2. it doesn't require -- as arguments separator.

Without (1) it complains as:

su: no such login class: exec "$0" "$@"

and without (2):

-: --: not found

Here, I've added detection of OS via uname -s which routes to the right su. I really think that other BSD may need it as well.

[weiss]

Thanks. Having no way to use su(1) in a portable manner keeps being a PITA.

-c before username is treated as login class;

I think this could be swapped on Linux as well (in which case -c $args is just handed over to the shell directly, rather than being parsed by su first, which seems just fine).

it doesn't require -- as arguments separator.

At first glance I'm unsure why we need the -- "$@" part at all, but I'm probably just overlooking something (I'll test things later).

I really think that other BSD may need it as well.

On other BSDs, there's the unrelated issue that they don't support -s "$SHELL" (unlike OpenBSD and Linux). For eturnal, I just omit that option on other systems and hope for the best (i.e., I hope the user running the service has a usable shell):

https://github.com/processone/eturnal/blob/1.12.1/overlay/eturnalctl#L157-L166

[catap]

I really think that other BSD may need it as well.

On other BSDs, there's the unrelated issue that they don't support -s "$SHELL" (unlike OpenBSD and Linux). For eturnal, I just omit that option on other systems and hope for the best (i.e., I hope the user running the service has a usable shell):

Probably something like this?

exec_cmd()
{
    case $EXEC_CMD,$(uname -s) in
        as_install_user,OpenBSD)
            su -s /bin/sh "$INSTALLUSER" -c 'exec "$0" "$@"' "$@"
            ;;
        as_install_user,Linux)
            su -s /bin/sh -c 'exec "$0" "$@"' "$INSTALLUSER" -- "$@"
            ;;
        as_install_user,*)
            su "$INSTALLUSER" "$@"
            ;;
        as_current_user,*)
            "$@"
            ;;
    esac
}

[coveralls]

coverage: 32.9%. remained the same
when pulling 1b77abc on catap:openbsd
into 7d0c20e on processone:master.