Post receive hook for Laravel website deploy

laravel_post_receive hook

#!/bin/bash

echo "********************"
echo "Post receive hook: Updating website"
echo "********************"

#set the git repo dir

GIT_REPO_DIR=~/git/<repo>.git
echo "The git repo dir is $GIT_REPO_DIR"



WEBROOT=/var/www/<website>
GIT_WORK_TREE=$WEBROOT git checkout -f
#change directory to the project dir
cd $WEBROOT

rm -f storage/cache/*
echo 'cache cleared'
rm -f storage/views/*
echo 'views cleared'

composer install

php artisan migrate --no-interaction

#Basset
#php artisan basset:build

#Bower
# only run if bower.json has changed 

echo "** Bower **"

# switch to webroot
cd $GIT_REPO_DIR

# geting a 'fatal: ambiguous argument' from this ?
#changedfiles=( `git diff-tree --no-commit-id --name-only HEAD@{1} HEAD` )

changedfiles=( `git diff-tree --no-commit-id --name-only HEAD^ HEAD` )
 
#switch back
cd $WEBROOT

# check if bower has been updated, if so install
if [[ "${changedfiles[*]}" =~ "bower.json" ]]; then
    echo "bower has been updated -  installing"
    bower install
    echo "bower pruning"
    bower prune
fi


# check if composer has been updated, if so install
# Check if the composer.lock file is present
if [[ "${changedfiles[*]}" =~ "composer.lock" ]]; then
        # Install or update packages specified in the lock file
        echo "composer.lock has been updated - do install"
        composer install --no-dev
fi


php artisan cache:clear

How to revert back the release to the previous commit?