Let install.php detect and inject extensions

For CI, I went with a dirty trick to find extensions and either
wfLoadExtension() or include them. That has since been ported to
Installer::findExtensions() and LocalSettingsGenerator::getText().

The WebInstaller() relies on that to detect extensions and let the user
tick the ones to be installed.

Add --with-extensions to install.php so one can include all extensions
from the command line.

Note: The CliInstaller always wfLoad() any skin it can find.

Bug: T189567
Change-Id: Ic8aa6bea4e7294e54fd5b71df267c9e934f78fce

RELEASE-NOTES-1.31

@@ -66,6 +66,8 @@ production.
     the SQL query. The ActorMigration class may also be used to get feature-flagged
     information needed to access actor-related fields during the migration
     period.
+* The CLI installer (maintenance/install.php) learned to detect and include
+  extensions. Pass --with-extensions to enable that feature.
 
 === External library changes in 1.31 ===
 

includes/installer/CliInstaller.php

@@ -107,6 +107,11 @@ class CliInstaller extends Installer {
 			$this->setVar( '_AdminPassword', $option['pass'] );
 		}
 
+		// Detect and inject any extension found
+		if ( isset( $options['with-extensions'] ) ) {
+			$this->setVar( '_Extensions', array_keys( $installer->findExtensions() ) );
+		}
+
 		// Set up the default skins
 		$skins = array_keys( $this->findExtensions( 'skins' ) );
 		$this->setVar( '_Skins', $skins );

maintenance/install.php

@@ -88,6 +88,8 @@ class CommandLineInstaller extends Maintenance {
 			false, true );
 		*/
 		$this->addOption( 'env-checks', "Run environment checks only, don't change anything" );
+
+		$this->addOption( 'with-extensions', "Detect and include extensions" );
 	}
 
 	public function getDbType() {