> I don't think that you should be forced to do it explicitely. If you want 
> to merge in another branch, you can do that _explicitely_. So, defaulting 
> to what most people want anyway is A Good Thing.

Here is a prototype patch to implement this functionality.  One problem 
is that config.c does not remove cleaned sections, so after "git-branch 
-d mybranch" one is left with a useless "[branch "mybranch"]" section in 
.git/config.  Other than this, it seems to work well in my experiments.

Paolo