If you like me are bothered by this bug:
Then you want to apply this little patch to tkdiff, that I attach.
Patch tkdiff to diff against base revision by default
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Thanks. Have you submitted it to the sourceforge tkdiff project too? They're back in independent action, and it will have to be applied over there to keep in sync.
I wouldn't want to change tkdiff's years-long behavior this way. I think people expect it to behave the way it does.