Put git_rails in /usr/local/bin/git_rails
Put the hooks in ~/.git_template/hooks
cd into the git repo you want to add it to and run cp -r ~/.git_template/hooks/ ./.git/hooks/
Now it will auto run migrations and bundle for you when you change branches!
If you get an error like .git/hooks/post-checkout: line 7: /usr/local/bin/git_rails: Permission denied, make sure your /usr/local/bin/git_rails has execute permissions. You can cd to the folder and run chmod +x git_rails.