git push stages original version on server

Hi all,

There's a thing I don't understand: I have a repository on a server from/to which I pull/push. But when I push to it, and do a checkout on the server, the pushed changes are not visible. It appears that the changed file is added to the index on the server automatically. Why is this? It seems dangerous. If I do a commit on the server, the changes from the client will be lost.

There's also a thing I'm not sure exists: I use a git server/client setup for developing a website. I would like git-pushes to appear immediately online (without having to ssh to the server and checking out manually). Is this possible?

My questions are:
- Why does git work like this?
- Can I change its behaviour (if I still want that after the answer to  
the previous question)?
- How can I have git automatically checkout pushed changes on the  
server?

Thanks in advance.

Kind regards,

Roald