(In reply to roland@rptd.ch from comment #13)
> I checked out the 18.2 branch which I assume should work (if the theory is
> correct).
> 
> Modifying files won't work with bisecting, right?

You'll probably have to 'git apply' the patch after each step, and 'git
checkout -f' before each time you do 'git bisect good/bad'