Add entry to Git log branches context menu

I want to create a plugin that adds an entry to the context menu when the user performs a right click on the branches in git log. What is the corresponding group id? 

Currently I only have the item in the context menu of the commits

    <extensions defaultExtensionNs="com.intellij">
    </extensions>

    <actions>
       <action id="GitlabMergeRequestAction"
               class="com.mypackage.myplugin.action.MyAction"
               text="Custom context menu entry">
               <add-to-group group-id="Git.Log.ContextMenu" anchor="first"/>
       </action>
    </actions>