Add feature flag for commit neighbor nav feature

app/assets/javascripts/diffs/components/app.vue

@@ -346,7 +346,7 @@ export default {
         }
       });
 
-      if (this.commit) {
+      if (this.commit && this.glFeatures.mrCommitNeighborNav) {
         Mousetrap.bind('c', () => this.moveToNeighboringCommit({ direction: 'next' }));
         Mousetrap.bind('x', () => this.moveToNeighboringCommit({ direction: 'previous' }));
       }

app/assets/javascripts/diffs/components/commit_item.vue

@@ -2,6 +2,8 @@
 import { mapActions } from 'vuex';
 import { GlButtonGroup, GlButton, GlIcon, GlTooltipDirective } from '@gitlab/ui';
 
+import glFeatureFlagsMixin from '~/vue_shared/mixins/gl_feature_flags_mixin';
+
 import UserAvatarLink from '~/vue_shared/components/user_avatar/user_avatar_link.vue';
 import Icon from '~/vue_shared/components/icon.vue';
 import ClipboardButton from '~/vue_shared/components/clipboard_button.vue';
@@ -48,6 +50,7 @@ export default {
   directives: {
     GlTooltip: GlTooltipDirective,
   },
+  mixins: [glFeatureFlagsMixin()],
   props: {
     commit: {
       type: Object,
@@ -160,7 +163,10 @@ export default {
             class="btn btn-default"
           />
         </div>
-        <div v-if="hasNeighborCommits" class="commit-nav-buttons ml-3">
+        <div
+          v-if="hasNeighborCommits && glFeatures.mrCommitNeighborNav"
+          class="commit-nav-buttons ml-3"
+        >
           <gl-button-group>
             <gl-button
               :href="previousCommitUrl"

app/controllers/projects/merge_requests_controller.rb

@@ -27,6 +27,7 @@ class Projects::MergeRequestsController < Projects::MergeRequests::ApplicationCo
     push_frontend_feature_flag(:widget_visibility_polling, @project, default_enabled: true)
     push_frontend_feature_flag(:merge_ref_head_comments, @project)
     push_frontend_feature_flag(:accessibility_merge_request_widget, @project)
+    push_frontend_feature_flag(:mr_commit_neighbor_nav, @project, default_enabled: true)
   end
 
   before_action do