Advice on merge tool

[Jan Vrany]

Hi there, 

I know this is not strictly speaking a Mercurial concern, but
maybe some of you may know...

I'm looking for a good non-interactive 3-way merge tool. 

Background: 
I have an automatic job that merges "default" branch into "my"
branch. So far I'm using Mercurial's builtin merge, but it often
fails to merge. When using KDiff3, it often succeeds and most of
the time is correct. So I;m quite happy with KDiff3's algorithm
(which is somehow "better" in my case). 

The problem is that KDuff3 cannot be (or - I don't know how)
configured to be completely non-interactive. I mean, when its 
merging magic fails, it opens a window and waits for the user
which is not what I want (since I run this as a CI job).

Any ideas? Preferably Linux, if it would be Windows-only, fine with 
me. 

Thanks a lot! 

Jan