#!/bin/bash
WORK_TREE="/var/www/example"
GIT_DIR="/var/repo/example.git"
BRANCH="master"

while read oldrev newrev ref
do
    # only checking out the master (or whatever branch you would like to deploy)
    if [ "$ref" = "refs/heads/$BRANCH" ];
    then
        echo "Ref $ref received. Deploying ${BRANCH} branch to production..."
        git --work-tree=$WORK_TREE --git-dir=$GIT_DIR checkout -f $BRANCH
        cd $WORK_TREE
        chown -R www-data:www-data $WORK_TREE
        chmod -R 744 $WORK_TREE
        composer install
    else
        echo "Ref $ref received. Doing nothing: only the ${BRANCH} branch may be deployed on this server."
    fi
done