$ git checkout upstream
$ rm -rf *
$ tar xf ~/tokyocabinet-1.1.15.tar.gz --strip 1
$ git add .
$ git commit -as

$ mv ~/tokyocabinet-1.1.15.tar.gz ../tokyocabinet_1.1.15.orig.tar.gz
$ pristine-tar commit ../tokyocabinet_1.1.15.orig.tar.gz `git rev-parse HEAD`

That's it