Disable submit button and dropdown when submitt comment form

app/assets/javascripts/notes.js

@@ -112,10 +112,17 @@ require('./task_list');
       // when issue status changes, we need to refresh data
       $(document).on("issuable:change", this.refresh);
 
+      $(document).on('submit', '.js-main-target-form', this.disableDropdown)
+
       // when a key is clicked on the notes
       return $(document).on("keydown", ".js-note-text", this.keydownNoteText);
     };
 
+    Notes.prototype.disableDropdown = function(e) {
+      const $form = $(e.target);
+      $form.find('.js-note-new-discussion').disable();
+    };
+
     Notes.prototype.cleanBinding = function() {
       $(document).off("ajax:success", ".js-main-target-form");
       $(document).off("ajax:success", ".js-discussion-note-form");

app/views/projects/notes/_comment_type_button.html.haml

 - noteable_type = @note.noteable_type
 
 .pull-left.btn-group.append-right-10.comment-type-dropdown.js-comment-type-dropdown
-  %button.btn.btn-nr.btn-create.comment-btn.js-comment-button.js-comment-submit-button
-    Comment
+  %input.btn.btn-nr.btn-create.comment-btn.js-comment-button.js-comment-submit-button{ type: 'submit', value: 'Comment' }
   - if @note.can_be_discussion_note?
     = button_tag type: 'button', class: 'btn btn-nr dropdown-toggle comment-btn js-note-new-discussion', data: { 'dropdown-trigger' => '#resolvable-comment-menu' } do
       = icon('caret-down')