Add git pre-push hook to check for TODO: in comments

todo.pre-push.sh

# create the pre-commit file & make it executable
touch .git/hooks/pre-commit
chmod +x .git/hooks/pre-commit

# The line below is important!
#!/bin/bash
# Don't push if TODO is in the source for HEAD 
dont_push_flag="TODO"

flag_found=`git grep --color "$dont_push_flag" HEAD`
if [ -n "$flag_found" ]
then
    # Display which commit the first occurence of the flag was found and exit failure
    commit=`git log --pretty=format:'%Cred%h%Creset' -S "$dont_push_flag" | tail -n1`
    echo "Found $flag_found, first occurence was in $commit, not pushing"
    exit 1
fi
exit 0