/usr/bin/git-obliterate is in git-extras 1.9.1-2.
This file is owned by root:root, with mode 0o755.
The actual contents of the file can be viewed below.
1 2 3 4 5 | #!/bin/sh
file=$1
test -z $file && echo "file required." 1>&2 && exit 1
git filter-branch -f --index-filter "git rm -r --cached $file --ignore-unmatch" --prune-empty --tag-name-filter cat -- --all
|