Add template only on new MR create page.

app/controllers/projects/merge_requests_controller.rb

@@ -80,6 +80,7 @@ class Projects::MergeRequestsController < Projects::ApplicationController
 
       @diffs = compare_action.diffs
       @merge_request.title = @merge_request.source_branch.titleize.humanize
+      @merge_request.description = @merge_request.target_project.merge_requests_template
       @target_project = @merge_request.target_project
       @target_repo = @target_project.repository
     end

app/views/projects/merge_requests/_form.html.haml

@@ -22,8 +22,7 @@
     .form-group
       = f.label :description, "Description", class: 'control-label'
       .col-sm-10
-        - template = @project.merge_requests_template
-        = f.text_area :description, value: template, class: "form-control js-gfm-input", rows: 14
+        = f.text_area :description, class: "form-control js-gfm-input", rows: 14
         %p.hint Description is parsed with #{link_to "GitLab Flavored Markdown", help_markdown_path, target: '_blank'}.
     %hr
     .form-group