$ git checkout --orphan NEWBRANCH
$ git rm -rf .
--orphan creates a new branch, but it starts without any commit. After running the above command you are on a new branch "NEWBRANCH", and the first commit you create from this state will start a new history without any ancestry.
You can then start adding files and commit them and they will live in their own branch. If you take a look at the log, you will see that it is isolated from the original log.
This is a bash script that will automatically turn your wifi off if you connect your computer to an ethernet connection and turn wifi back on when you unplug your ethernet cable/adapter. If you decide to turn wifi on for whatever reason, it will remember that choice. This was improvised from this mac hint to work with Yosemite, and without hard-coding the adapter names. It's supposed to support growl, but I didn't check that part. I did, however, add OSX notification center support. Feel free to fork and fix any issues you encounter.
Most the credit for these changes go to Dave Holland.