Correctly remove the charset from finfo mimetype

lib/private/Files/Type/Detection.php

@@ -200,7 +200,7 @@ class Detection implements IMimeTypeDetector {
 			$info = @strtolower(finfo_file($finfo, $path));
 			finfo_close($finfo);
 			if ($info) {
-				$mimeType = substr($info, 0, strpos($info, ';'));
+				$mimeType = strpos($info, ';') !== false ? substr($info, 0, strpos($info, ';')) : $info;
 				return empty($mimeType) ? 'application/octet-stream' : $mimeType;
 			}
 
@@ -238,7 +238,8 @@ class Detection implements IMimeTypeDetector {
 	public function detectString($data) {
 		if (function_exists('finfo_open') and function_exists('finfo_file')) {
 			$finfo = finfo_open(FILEINFO_MIME);
-			return finfo_buffer($finfo, $data);
+			$info = finfo_buffer($finfo, $data);
+			return strpos($info, ';') !== false ? substr($info, 0, strpos($info, ';')) : $info;
 		} else {
 			$tmpFile = \OC::$server->getTempManager()->getTemporaryFile();
 			$fh = fopen($tmpFile, 'wb');

tests/lib/Files/Type/DetectionTest.php

@@ -81,7 +81,7 @@ class DetectionTest extends \Test\TestCase {
 
 	public function testDetectString() {
 		$result = $this->detection->detectString("/data/data.tar.gz");
-		$expected = 'text/plain; charset=us-ascii';
+		$expected = 'text/plain';
 		$this->assertEquals($expected, $result);
 	}