Helper function to get a git commit hash from a few sources.

get_commit_hash.php

<?php

if (!function_exists('get_commit_hash')) {
   /**
    * Checks to see if we have a .commit_hash file or .git repo and return the hash if we do.
    *
    * @return null|string
    */
   function get_commit_hash()
   {
       $commitHash = base_path('.commit_hash');

       if (file_exists($commitHash)) {
           // See if we have the .commit_hash file
           return trim(exec(sprintf('cat %s', $commitHash)));
       } elseif (is_dir(base_path('.git'))) {
           // Do we have a .git repo?
           return trim(exec('git log --pretty="%h" -n1 HEAD'));
       } else {
           // ¯\_(ツ)_/¯
           return null;
       }
   }
}