Don't treat "/" as valid ignore pattern

This matches the behavior of C Git.

Bug: 415767
Change-Id: Ifa6500f3f6a033da40c48287630b77c47b15f4a0
Signed-off-by: Robin Stocker <robin@nibor.org>

org.eclipse.jgit.test/tst/org/eclipse/jgit/ignore/IgnoreNodeTest.java

@@ -166,6 +166,17 @@ public class IgnoreNodeTest extends RepositoryTestCase {
 		assertEntry(F, tracked, "src/a/b");
 	}
 
+	@Test
+	public void testNoPatterns() throws IOException {
+		writeIgnoreFile(".gitignore", "", " ", "# comment", "/");
+		writeTrashFile("a/a", "");
+
+		beginWalk();
+		assertEntry(F, tracked, ".gitignore");
+		assertEntry(D, tracked, "a");
+		assertEntry(F, tracked, "a/a");
+	}
+
 	private void beginWalk() throws CorruptObjectException {
 		walk = new TreeWalk(db);
 		walk.addTree(new FileTreeIterator(db));

org.eclipse.jgit/src/org/eclipse/jgit/ignore/IgnoreNode.java

@@ -102,7 +102,7 @@ public class IgnoreNode {
 		String txt;
 		while ((txt = br.readLine()) != null) {
 			txt = txt.trim();
-			if (txt.length() > 0 && !txt.startsWith("#")) //$NON-NLS-1$
+			if (txt.length() > 0 && !txt.startsWith("#") && !txt.equals("/")) //$NON-NLS-1$ //$NON-NLS-2$
 				rules.add(new IgnoreRule(txt));
 		}
 	}