Let CloneCommand not checkout HEAD on bare repos

If the clone command clones into a bare repository it should not try
to checkout HEAD in the end. For bare repos checkout is not possible.

Change-Id: I359719d421b93c9d2e962e3c0eccc2b59235c3d1
Signed-off-by: Christian Halstrick <christian.halstrick@sap.com>

org.eclipse.jgit/src/org/eclipse/jgit/api/CloneCommand.java

@@ -177,9 +177,12 @@ public class CloneCommand implements Callable<Git> {
 		u.setNewObjectId(commit.getId());
 		u.forceUpdate();
 
-		DirCache dc = repo.lockDirCache();
-		DirCacheCheckout co = new DirCacheCheckout(repo, dc, commit.getTree());
-		co.checkout();
+		if (!bare) {
+			DirCache dc = repo.lockDirCache();
+			DirCacheCheckout co = new DirCacheCheckout(repo, dc,
+					commit.getTree());
+			co.checkout();
+		}
 	}
 
 	private RevCommit parseCommit(final Repository repo, final Ref ref)