Drupal branch-specific database settings

settings.php

<?php
// full path to project root (you'll need to edit this)
$root = dirname(dirname(dirname(__DIR__)));

// project name here (full db name will be my_project_[current git branch])
$project_name = 'my_project';

// base connection info
$base_conn = array(
  'driver' => 'mysql',
  'username' => 'USERNAME',
  'password' => 'PASSWORD',
  'host' => 'localhost',
  'prefix' => '',
);

// set the database name based on which git branch we're in
$branch = file($root . '/.git/HEAD');
$branch = reset($branch);
$branch = explode('/', $branch);
$branch = trim($branch[2]);
$databases['default']['default'] = $base_conn + array(
  'database' => $project_name . '_' . $branch,
);