Feature Request: filter included/served files based on browser

This might be a duplicate --- I searched but there were a lot of issues, hard to narrow it down effectively and quickly.

So, it's possible to work around this with multiple karma configurations, but it would be really nice if you could say "load file X if the browser is not Y or Z, otherwise load browser Ε".

Use case: loading sinon-ie as well as sinon, so that when IE runs would load the appropriate version, and non-IE runs would also load the appropriate version. This would be a kind of filtering behaviour, I guess.

I'm not really expecting this to be implemented, but it would be nice, and a lot more elegant than having per-browser karma configurations.