How to specify config file in .desktop file?

Hi

I added a new desktop file (below) to the xsessions directory to start with a non-default awesone
config file, and everything is working now, but I am not happy that I have to specify the complete
path in the -c : I tried

Exec=awesome -c ~/.config/awesome/rc.shifty.lua
Exec=awesome -c $HOME/.config/awesome/rc.shifty.lua

in the assumption that this would be evaluated after the variables are set, but this is not the
case - in both cases, the file rc.shifty.lua was not found. Only when using, as below,

Exec=awesome -c /home/rkrug/.config/awesome/rc.shifty.lua

it worked.

This is not a problem as I am the only user, but I would like to know what the best way is to
specify the awesome config file.

Cheers,

Rainer

$ cat /usr/share/xs
xscreensaver/ xserver-xorg/ xsessions/
rkrug <at> ecolmod:~$ cat /usr/share/xse
xserver-xorg/ xsessions/
rkrug <at> ecolmod:~$ cat /usr/share/xsessions/awesome
awesome.desktop         awesome_shifty.desktop
rkrug <at> ecolmod:~$ cat /usr/share/xsessions/awesome_shifty.desktop
[Desktop Entry]
Encoding=UTF-8
Name=awesome shifty
Comment=Highly configurable framework window manager
TryExec=awesome
Exec=awesome -c /home/rkrug/.config/awesome/rc.shifty.lua