Fix DirCache,getEntriesWithin for empty string arguemnt

Change-Id: I0bea130df611de3ef8c9251093b11c62b5442cd1

org.eclipse.jgit.test/tst/org/eclipse/jgit/dircache/DirCacheFindTest.java

@@ -88,6 +88,13 @@ public class DirCacheFindTest extends RepositoryTestCase {
 			for (int i = aFirst, j = 0; i <= aLast; i++, j++)
 				assertSame(ents[i], aContents[j]);
 		}
+		{
+			final DirCacheEntry[] aContents = dc.getEntriesWithin("");
+			assertNotNull(aContents);
+			assertEquals(ents.length, aContents.length);
+			for (int i = 0; i < ents.length; i++)
+				assertSame(ents[i], aContents[i]);
+		}
 
 		assertNotNull(dc.getEntriesWithin("a."));
 		assertEquals(0, dc.getEntriesWithin("a.").length);

org.eclipse.jgit/src/org/eclipse/jgit/dircache/DirCache.java

@@ -712,6 +712,11 @@ public class DirCache {
 	 * @return all entries recursively contained within the subtree.
 	 */
 	public DirCacheEntry[] getEntriesWithin(String path) {
+		if (path.length() == 0) {
+			final DirCacheEntry[] r = new DirCacheEntry[sortedEntries.length];
+			System.arraycopy(sortedEntries, 0, r, 0, sortedEntries.length);
+			return r;
+		}
 		if (!path.endsWith("/"))
 			path += "/";
 		final byte[] p = Constants.encode(path);