Dumps duplicated directories tracked by git. Dependent on a package `symfony/process`.

git-directory-duplicates.php

<?php

require __DIR__ . '/../vendor/autoload.php';

$duplicates = (static function (array $paths) {
	$directories = [[]];

	foreach ($paths as $path) {
		$directories[] = (static function (string $path) {
			$process = Symfony\Component\Process\Process::fromShellCommandline('git ls-tree -r --name-only HEAD "$TREE_PATH"');
			$directories = [];

			$process->run(static function (string $type, string $output) use (&$directories) {
				if (Symfony\Component\Process\Process::OUT !== $type) {
					throw new RuntimeException('Can not read a git tree.');
				}

				$directories = array_merge(
					$directories,
					array_unique(
						array_map(static function (string $path) {
							return dirname($path);
						}, explode("\n", $output))
					)
				);
			}, ['TREE_PATH' => $path]);

			return $directories;
		})($path);
	}

	$directories = array_unique(array_merge(...$directories));
	$duplicates = [];

	foreach ($directories as $directory) {
		$duplicates[strtolower($directory)][] = $directory;
	}

	return array_values(array_filter($duplicates, static function (array $dirs) {
		return 1 < count($dirs);
	}));
})([
	__DIR__ . '/../src',
	__DIR__ . '/../extensions',
]);

var_dump($duplicates);