commiting while the current version is in conflict

Hi all,

I fooled around with git a liitle bit and noticed something rather strange. I merged two branches, creating a conflict on purpose. When I then did a

 git commit -a

all changes were submitted. Of course, I now have a file with the conflict markers inlined in my repository. Not a good thing, imo. Is there a way to make git block all conflicting versions?

Also, I would be interested in the design decissions behind the current behaviour. Any pointers?

Thanks, Richard