Upgrade/Install: Initialize the local $checkout variable in WP_Automatic_Updater::is_vcs_checkout().

This avoids an `Undefined variable $checkout` PHP warning if all of the directories checked for access are disallowed due to the PHP `open_basedir` restrictions.

Follow-up to [55425].

Props jqz, costdev, audrasjb.
Fixes #58563.

git-svn-id: https://develop.svn.wordpress.org/trunk@56124 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-admin/includes/class-wp-automatic-updater.php

@@ -148,6 +148,7 @@ class WP_Automatic_Updater {
 		}
 
 		$check_dirs = array_unique( $check_dirs );
+		$checkout   = false;
 
 		// Search all directories we've found for evidence of version control.
 		foreach ( $vcs_dirs as $vcs_dir ) {

tests/phpunit/tests/admin/wpAutomaticUpdater.php

@@ -706,4 +706,28 @@ class Tests_Admin_WpAutomaticUpdater extends WP_UnitTestCase {
 			'string with only carriage returns' => array( 'dir' => "\r\r" ),
 		);
 	}
+
+	/**
+	 * Tests that `WP_Automatic_Updater::is_vcs_checkout()` returns `false`
+	 * when none of the checked directories are allowed.
+	 *
+	 * @ticket 58563
+	 *
+	 * @covers WP_Automatic_Updater::is_vcs_checkout
+	 */
+	public function test_is_vcs_checkout_should_return_false_when_no_directories_are_allowed() {
+		$updater_mock = $this->getMockBuilder( 'WP_Automatic_Updater' )
+			// Note: setMethods() is deprecated in PHPUnit 9, but still supported.
+			->setMethods( array( 'is_allowed_dir' ) )
+			->getMock();
+
+		/*
+		 * As none of the directories should be allowed, simply mocking `WP_Automatic_Updater`
+		 * and forcing `::is_allowed_dir()` to return `false` removes the need to run the test
+		 * in a separate process due to setting the `open_basedir` PHP directive.
+		 */
+		$updater_mock->expects( $this->any() )->method( 'is_allowed_dir' )->willReturn( false );
+
+		$this->assertFalse( $updater_mock->is_vcs_checkout( get_temp_dir() ) );
+	}
 }