Slim deployment with git archive for deployment tutorial here: https://baapwp.me/2017/04/15/creating-simple-deployment-script-php/

webhook-slim.php

<?php

$repositories = array(
	'custom-theme' => array(
		'git_url' => '[email protected]/yapapaya/custom-theme.git',
		'branch' => 'master',
		'path' => '/var/www/dev.yoursite.com/htdocs/wp-content/themes/',
	),
	'custom-plugin' => array(
		'git_url' => '[email protected]/yapapaya/custom-plugin.git',
		'branch' => 'master',
		'path' => '/var/www/dev.yoursite.com/htdocs/wp-content/plugins/'
	),
);

if ( ! is_dir( '/var/www/dev.yoursite.com/htdocs/repositories/' ) ) {
	mkdir( '/var/www/dev.yoursite.com/htdocs/repositories/' );
}

$original_dir = getcwd();


foreach ( $repositories as $repo_name => $repo ) {

	$deploy_path = $repo[ 'path' ] . '/' . $repo_name;

	if ( ! is_dir( $deploy_path ) ) {
		mkdir( $deploy_path );
	}

	exec( "git archive --remote={$repo[ 'git_url' ]} {$repo[ 'branch' ]} | (cd " . $deploy_path . " && tar -x)" );

	chdir( $original_dir );
}