How do I stop SemanticMerge from displaying an unsupported language warning when diffing?

How can I configure SemanticMerge to not display a warning dialog when diffing files in a not supported language? By default, when asked to diff files in a language it doesn't understand, it'll display a dialog as pictured below:

Warning dialog

I'd like to configure the default behaviour to correspond to the left button in the dialog, i.e. perform text diff.

Solution

SemanticMerge has a commandline option for this purpose, --nolangwarn. For example, in my Git configuration file I've configured SemanticMerge for diffing like so:

[difftool "semanticdiff"]
    cmd = C:/Users/Arve/AppData/Local/PlasticSCM4/semanticmerge/semanticmergetool.exe -d \"$REMOTE\" -s \"$LOCAL\" --nolangwarn