Highlight the HEAD ref in the list of branches

Move it to the top and make it bold, if it exists. Only applies to the
leaf branch of the HEAD symbolic ref, not to non-branches or
non-symbolic referents of HEAD.

Change-Id: Idcac9fca76c079a7c0f5fe5149175d1065c48fee

gitiles-servlet/src/main/java/com/google/gitiles/RepositoryIndexServlet.java

diff --git a/gitiles-servlet/src/main/java/com/google/gitiles/RepositoryIndexServlet.java b/gitiles-servlet/src/main/java/com/google/gitiles/RepositoryIndexServlet.java
index 79f90e9..eb61a25 100644
--- a/gitiles-servlet/src/main/java/com/google/gitiles/RepositoryIndexServlet.java
+++ b/gitiles-servlet/src/main/java/com/google/gitiles/RepositoryIndexServlet.java
@@ -64,7 +64,7 @@
     Repository repo = ServletUtils.getRepository(req);
     RepositoryDescription desc = accessFactory.forRequest(req).getRepositoryDescription();
     RevWalk walk = new RevWalk(repo);
-    List<Map<String, String>> tags;
+    List<Map<String, Object>> tags;
     Map<String, Object> data;
     try {
       tags = RefServlet.getTags(req, timeCache, walk, REF_LIMIT);
@@ -88,7 +88,7 @@
     if (!data.containsKey("entries")) {
       data.put("entries", ImmutableList.of());
     }
-    List<Map<String, String>> branches = RefServlet.getBranches(req, REF_LIMIT);
+    List<Map<String, Object>> branches = RefServlet.getBranches(req, REF_LIMIT);
 
     data.put("cloneUrl", desc.cloneUrl);
     data.put("mirroredFromUrl", Strings.nullToEmpty(desc.mirroredFromUrl));