Stop breadcrumbs changing container when in side-by-side diff

app/assets/javascripts/merge_request_tabs.js

@@ -352,7 +352,7 @@ import {
     }
 
     expandViewContainer() {
-      const $wrapper = $('.content-wrapper .container-fluid');
+      const $wrapper = $('.content-wrapper .container-fluid').not('.breadcrumbs');
       if (this.fixedLayoutPref === null) {
         this.fixedLayoutPref = $wrapper.hasClass('container-limited');
       }

changelogs/unreleased/mr-side-by-side-breadcrumbs-container.yml

+---
+title: Fixed breadcrumbs container expanding in side-by-side diff view
+merge_request:
+author:
+type: fixed

spec/javascripts/merge_request_tabs_spec.js

@@ -416,5 +416,28 @@ import 'vendor/jquery.scrollTo';
         });
       });
     });
+
+    describe('expandViewContainer', function () {
+      beforeEach(() => {
+        $('body').append('<div class="content-wrapper"><div class="container-fluid container-limited"></div></div>');
+      });
+
+      afterEach(() => {
+        $('.content-wrapper').remove();
+      });
+
+      it('removes container-limited from containers', function () {
+        this.class.expandViewContainer();
+
+        expect($('.content-wrapper')).not.toContainElement('.container-limited');
+      });
+
+      it('does remove container-limited from breadcrumbs', function () {
+        $('.container-limited').addClass('breadcrumbs');
+        this.class.expandViewContainer();
+
+        expect($('.content-wrapper')).toContainElement('.container-limited');
+      });
+    });
   });
 }).call(window);