Notification when switching to git branches with different composer.lock source: http://www.markbadolato.com/blog/2013/08/23/notification-when-switchin-git-branches/

post-checkout

#!/bin/bash
# wget https://gist.github.com/drymek/6896918/raw -O /usr/share/git-core/templates/hooks/post-checkout
# chmod +x /usr/share/git-core/templates/hooks/post-checkout
# git init # to reload current git repository

PREV_COMMIT=$1
POST_COMMIT=$2

# MacOS Colors
NOCOLOR='\x1B[0m'
REDCOLOR='\x1B[37;41m'

# Linux Colors
#NOCOLOR='\e[0m'
#REDCOLOR='\e[37;41m'

if [[ -f composer.lock ]]; then
    DIFF=`git diff --shortstat $PREV_COMMIT..$POST_COMMIT composer.lock`
    if [[ $DIFF != "" ]]; then
        echo -e "\n${REDCOLOR}                                                                  $NOCOLOR";
        echo -e "${REDCOLOR}    composer.lock has changed. You should run composer install    $NOCOLOR";
        echo -e "${REDCOLOR}                                                                  $NOCOLOR\n";
    fi
fi