Bash script to install a `pre-push-hook` into the current git repo

install-pre-push-hook.sh

#!/usr/bin/env bash
# install-pre-push-hook
# this script installs the pre-push hook into the current .git repo.
# by default, the pre-push hook protects the "master" branch.
set_git_hooks_dir_path() {
  set_git_dir_path
  git_hooks_dir_path="$git_dir_path/hooks"
  if [[ ! -d "$git_hooks_dir_path" ]] ; then
    echo 1>&2 "$git_hooks_dir_path does not exist!"
    exit
  fi
}
set_git_dir_path() {
  local dir_path=`git rev-parse --git-dir`
  git_dir_path=`absolute_path "$dir_path"`
  if [[ ! -d "$git_dir_path" ]]; then
    echo 1>&2 "Not in a repo!"
    exit
  fi
}
absolute_path() {
  case "$1" in
    /*) echo "$1" ;;
    *)  echo "`pwd`/$1" ;;
  esac
}
install_pre_push_script() {
  set_git_hooks_dir_path
  pre_push_path="$git_hooks_dir_path/pre-push"
  if [[ -e "$pre_push_path" ]]  ; then
    mv "$pre_push_path" "$pre_push_path.old"
  fi
  create_pre_push_script "$pre_push_path"
}
create_pre_push_script() {
  local dest_path="$1"
  cat <<'EOF' >"$dest_path"
#!/bin/bash
protected_branch='master'
current_branch=$(git symbolic-ref HEAD | sed -e 's,.*/\(.*\),\1,')
if [ $protected_branch = $current_branch ] ; then
  read -p "You're about to push master, is that what you intended? [y|n] " -n 1 -r < /dev/tty
  echo
  if echo $REPLY | grep -E '^[Yy]$' > /dev/null ; then
    exit 0              # push will execute
  fi
  exit 1                # push will not execute
fi
exit 0                  # push will execute
EOF
  chmod +x $dest_path
  echo 1>&2 "Created $dest_path"
}
install_pre_push_script
exit