[log] Expose VcsLogRefs into API

* For now just return branches, since it is all what's needed.
* Keep getRefsModel() until it is decided what methods should be exposed

platform/vcs-log/api/src/com/intellij/vcs/log/VcsLogDataPack.java

@@ -25,4 +25,7 @@ public interface VcsLogDataPack {
   @NotNull
   Map<VirtualFile, VcsLogProvider> getLogProviders();
 
+  @NotNull
+  VcsLogRefs getRefs();
+
 }

platform/vcs-log/api/src/com/intellij/vcs/log/VcsLogRefs.java

@@ -0,0 +1,33 @@
+/*
+ * Copyright 2000-2014 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.intellij.vcs.log;
+
+import org.jetbrains.annotations.NotNull;
+
+import java.util.Collection;
+
+/**
+ * Collection of {@link VcsRef branches & tags references} which are in the log.
+ */
+public interface VcsLogRefs {
+
+  /**
+   * Returns all branches.
+   */
+  @NotNull
+  Collection<VcsRef> getBranches();
+
+}

platform/vcs-log/impl/src/com/intellij/vcs/log/data/DataPack.java

@@ -75,6 +75,12 @@ public class DataPack implements VcsLogDataPack {
     return myGraphFacade;
   }
 
+  @NotNull
+  @Override
+  public VcsLogRefs getRefs() {
+    return myRefsModel;
+  }
+
   @NotNull
   public RefsModel getRefsModel() {
     return myRefsModel;

platform/vcs-log/impl/src/com/intellij/vcs/log/data/RefsModel.java

@@ -6,6 +6,7 @@ import com.intellij.util.SmartList;
 import com.intellij.util.containers.ContainerUtil;
 import com.intellij.util.containers.MultiMap;
 import com.intellij.vcs.log.Hash;
+import com.intellij.vcs.log.VcsLogRefs;
 import com.intellij.vcs.log.VcsRef;
 import gnu.trove.TIntObjectHashMap;
 import org.jetbrains.annotations.NotNull;
@@ -14,10 +15,7 @@ import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
 
-/**
- * @author erokhins
- */
-public class RefsModel {
+public class RefsModel implements VcsLogRefs {
 
   @NotNull private final Collection<VcsRef> myBranches;
   @NotNull private final MultiMap<Hash, VcsRef> myRefsToHashes;
@@ -80,6 +78,7 @@ public class RefsModel {
     return myRefsToIndices.containsKey(index) ? myRefsToIndices.get(index) : Collections.<VcsRef>emptyList();
   }
 
+  @Override
   @NotNull
   public Collection<VcsRef> getBranches() {
     return myBranches;