tatt just runs every time emerge -1v . If you want, you can add a quiet(or similar) use flag that will do a sed like this "s:-1v:-1q"
This should probably be a runtime option, not a USE-flag, right? I'll add it to the tatt configuration capabilities.
This is fixed. Thanks for the suggestion. Except "-1" there are no further options passed to emerge by default. Using the variable "emergeopts" in your ~/.tatt you can configure other options that you like.