Fix mimetype detection inside hidden folders (#26138)

Downstreaming of https://github.com/owncloud/core/pull/26138

Signed-off-by: Lukas Reschke <lukas@statuscode.ch>

lib/private/Files/Type/Detection.php

@@ -166,9 +166,11 @@ class Detection implements IMimeTypeDetector {
 	public function detectPath($path) {
 		$this->loadMappings();
 
-		if (strpos($path, '.')) {
+		$fileName = basename($path);
+		// note: leading dot doesn't qualify as extension
+		if (strpos($fileName, '.') > 0) {
 			//try to guess the type by the file extension
-			$extension = strtolower(strrchr(basename($path), "."));
+			$extension = strtolower(strrchr($fileName, '.'));
 			$extension = substr($extension, 1); //remove leading .
 			return (isset($this->mimetypes[$extension]) && isset($this->mimetypes[$extension][0]))
 				? $this->mimetypes[$extension][0]

tests/lib/Files/Type/DetectionTest.php

@@ -74,6 +74,8 @@ class DetectionTest extends \Test\TestCase {
 		$this->assertEquals('text/plain', $this->detection->detectPath('foo.txt'));
 		$this->assertEquals('image/png', $this->detection->detectPath('foo.png'));
 		$this->assertEquals('image/png', $this->detection->detectPath('foo.bar.png'));
+		$this->assertEquals('image/png', $this->detection->detectPath('.hidden/foo.png'));
+		$this->assertEquals('image/png', $this->detection->detectPath('test.jpg/foo.png'));
 		$this->assertEquals('application/octet-stream', $this->detection->detectPath('.png'));
 		$this->assertEquals('application/octet-stream', $this->detection->detectPath('foo'));
 		$this->assertEquals('application/octet-stream', $this->detection->detectPath(''));