pre-push.sh

#!/bin/sh

# Called by "git push" after it has checked the remote status,
# but before anything has been pushed.
#
# If this script exits with a non-zero status nothing will be pushed.
#
# Steps to install, from the root directory of your repo...
# 1. Copy the file into your repo at `.git/hooks/pre-push`
# 2. Set executable permissions, run `chmod +x .git/hooks/pre-push`
# 3. Or, use `rake hooks:pre_push` to install
#
# Try a force push to master, you should get a message `*** [Policy] never force push...`
#
# The commands below will not be allowed...
# `git push --force origin master`
# `git push --delete origin master`
# `git push origin :master`
#
# Nor will a force push while on the master branch be allowed...
# `git co master`
# `git push --force origin`
#
# Requires git 1.8.2 or newer
#
# Git 1.8.2 release notes cover the new pre-push hook:
# <https://github.com/git/git/blob/master/Documentation/RelNotes/1.8.2.txt>
#
# See Sample pre-push script:
# <https://github.com/git/git/blob/87c86dd14abe8db7d00b0df5661ef8cf147a72a3/templates/hooks--pre-push.sample>

# Allows us to read user input below, assigns stdin to keyboard
exec < /dev/tty

PUSH_COMMAND=$(ps -ocommand= -p $PPID)

IS_DESTRUCTIVE='force|delete|\-f'

confirm() {
  while true; do
    read -p "Are you sure you want to force push? " yn
    case $yn in
        [Yy]* ) return 0; break;;
        [Nn]* ) return 1;;
        * ) echo "Please answer yes or no.";;
    esac
  done
}

if [[ $PUSH_COMMAND =~ $IS_DESTRUCTIVE ]]; then
  confirm
fi

RETURN_CODE=$?

unset confirm

exit $RETURN_CODE