title: gitlab API gitlab4j Java change default branche
body: <p>I'm using <code>gitlab4j</code>to change project default branch from <code>master</code> to <code>dev</code> with Java, I have authenticated changed the default branch but changes not saved</p>
  
  <pre class="lang-java prettyprint-override"><code>GitLabApi gitLabApi = new GitLabApi("***", "mytoken");
  List&lt;Project&gt; projects = gitLabApi.getProjectApi().getProjects();
  
  for (Project project : projects) {
      if(project.getId()==633) {
          project.setDefaultBranch("dev");            
      }
  }
  </code></pre>