Fix endless loop in ObjectChecker for MacOS

Bug: 477090
Change-Id: I0ba416f1cc172a835dd2723ff7fa904597ffd097
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

org.eclipse.jgit.test/tst/org/eclipse/jgit/lib/ObjectCheckerTest.java

@@ -1809,6 +1809,17 @@ public class ObjectCheckerTest {
 		}
 	}
 
+	@Test
+	public void testBug477090() throws CorruptObjectException {
+		checker.setSafeForMacOS(true);
+		final byte[] bytes = {
+				// U+221E 0xe2889e INFINITY ∞
+				(byte) 0xe2, (byte) 0x88, (byte) 0x9e,
+				// .html
+				0x2e, 0x68, 0x74, 0x6d, 0x6c };
+		checker.checkPathSegment(bytes, 0, bytes.length);
+	}
+
 	@Test
 	public void testRejectDotAtEndOnWindows() {
 		checker.setSafeForWindows(true);

org.eclipse.jgit/src/org/eclipse/jgit/lib/ObjectChecker.java

@@ -618,8 +618,9 @@ public class ObjectChecker {
 					default:
 						return false;
 					}
+				default:
+					return false;
 				}
-				break;
 			case (byte) 0xef: // http://www.utf8-chartable.de/unicode-utf8-table.pl?start=65024
 				checkTruncatedIgnorableUTF8(raw, ptr, end);
 				// U+FEFF 0xefbbbf ZERO WIDTH NO-BREAK SPACE