Add git tools

[jdarwood007]

Add git information. Add a way to select what packages we want to see git status for

I already do this on my git checkout for SMF

I should add a sections saying "clean" or "modified" to indicate if files are all clean or modified. Should be easy enough with checking the git status --porcelain output.
This will require shell_exec permissions.

[jdarwood007]

Keeping track of my current notes.
The current method is add to Settings.php:

define('GITSITE', dirname(__FILE__));
require_once('smf_git_info.php');

Then smf_git_info.php contains

register_shutdown_function('__pseudo_smf_git_handle');

function __pseudo_smf_git_handle()
{
	$contents = ob_get_contents();
	ob_clean();

	if (defined('GITSITE') && php_sapi_name() != 'cli')
	{
		chdir(GITSITE);

		// Current branch
		$smf_git_current_branch = rtrim(shell_exec("git status | grep 'On branch' | awk '{print $3}'") ?? '');
		$smf_git_current_revision = rtrim(shell_exec('git log -n1 | grep -E \'^commit [A-Za-z0-9]{40}$\' | awk \'{print $2}\'') ?? '');
		$smf_git_modified_files = rtrim(shell_exec('git status --porcelain') ?? '');

		$contents = preg_replace('~Simple Machines</a></li>~i', 'Simple Machines</a></li>
				<li class="smalltext">SMF [Git Branch: ' . $smf_git_current_branch . ' | Git Revision: ' . substr($smf_git_current_revision, -7) . ' | ' . (!empty($smf_git_modified_files) ? 'Modified Files' : 'Clean Files') . ']</li>', $contents);
	}

	echo $contents;
}

Will need cleanup for going into tools.