gitlabhq/app/views/tree/edit.html.haml

.file-editor
  = form_tag(project_tree_path(@project, @id), :method => :put) do
    .file_holder
      .file_title
        %i.icon-file
        %span.file_name
          = "#{@tree.path.force_encoding('utf-8')} (#{@ref})"
      .file_content.code
        #editor= @tree.data

    .editor-commit-comment
      = label_tag 'commit_message' do
        %p.slead Commit message
      = text_area_tag 'commit_message', '', :required => true
    .form-actions
      = hidden_field_tag 'last_commit', @last_commit
      = hidden_field_tag 'content', '', :id => :file_content
      = button_tag "Commit", class: 'btn save-btn'
      = link_to "Cancel", project_tree_path(@project, @id), class: "btn cancel-btn", confirm: "Are you sure?"

:javascript
  var editor = ace.edit("editor");
  editor.getSession().setMode("ace/mode/javascript");

  $(".save-btn").click(function(){
    $("#file_content").val(editor.getValue());
    $(".form_editor form").submit();
  });