Fix tabs navigation and do not update URL via pushstate

app/assets/javascripts/merge_request_tabs.js

@@ -15,6 +15,7 @@
 
     function MergeRequestTabs(opts) {
       this.opts = opts != null ? opts : {};
+      this.opts.setUrl = this.opts.setUrl !== undefined ? this.opts.setUrl : true;
       this.setCurrentAction = bind(this.setCurrentAction, this);
       this.tabShown = bind(this.tabShown, this);
       this.showTab = bind(this.showTab, this);
@@ -58,7 +59,9 @@
       } else {
         this.expandView();
       }
-      return this.setCurrentAction(action);
+      if (this.opts.setUrl) {
+        this.setCurrentAction(action);
+      }
     };
 
     MergeRequestTabs.prototype.scrollToElement = function(container) {

app/controllers/projects/merge_requests_controller.rb

@@ -216,7 +216,7 @@ class Projects::MergeRequestsController < Projects::ApplicationController
     @base_commit = @merge_request.diff_base_commit
     @diffs = @merge_request.diffs(diff_options) if @merge_request.compare
     @diff_notes_disabled = true
-
+    @show_diff_tab = check_diff_tab
     @pipeline = @merge_request.pipeline
     @statuses = @pipeline.statuses.relevant if @pipeline
 
@@ -520,4 +520,10 @@ class Projects::MergeRequestsController < Projects::ApplicationController
     params[:merge_request] ||= ActionController::Parameters.new(source_project: @project)
     @merge_request = MergeRequests::BuildService.new(project, current_user, merge_request_params).execute
   end
+
+  private
+
+  def check_diff_tab
+    request.query_parameters[:view].present?
+  end
 end

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

@@ -20,7 +20,7 @@
 .mr-compare.merge-request
   %ul.merge-request-tabs.nav-links.no-top.no-bottom
     %li.commits-tab
-      = link_to url_for(params), data: {target: 'div#commits', action: 'commits', toggle: 'tab'} do
+      = link_to url_for(params), data: {target: 'div#commits', action: 'new', toggle: 'tab'} do
         Commits
         %span.badge= @commits.size
     - if @pipeline
@@ -52,11 +52,8 @@
     $('#merge_request_assignee_id').val("#{current_user.id}").trigger("change");
     e.preventDefault();
   });
-
 :javascript
-  var merge_request
-  merge_request = new MergeRequest({
-    action: 'new',
-    diffs_loaded: true,
-    commits_loaded: true
+  var merge_request = new MergeRequest({
+    action: "#{(@show_diff_tab ? 'diffs' : 'new')}",
+    setUrl: false 
   });