Changing yaml file to true and adding default_enabled to feature checks

app/controllers/projects/merge_requests_controller.rb

@@ -36,7 +36,7 @@ class Projects::MergeRequestsController < Projects::MergeRequests::ApplicationCo
     push_frontend_feature_flag(:merge_request_widget_graphql, @project)
     push_frontend_feature_flag(:drag_comment_selection, @project, default_enabled: true)
     push_frontend_feature_flag(:unified_diff_components, @project, default_enabled: true)
-    push_frontend_feature_flag(:default_merge_ref_for_diffs, @project)
+    push_frontend_feature_flag(:default_merge_ref_for_diffs, @project, default_enabled: :yaml)
     push_frontend_feature_flag(:core_security_mr_widget_counts, @project)
     push_frontend_feature_flag(:remove_resolve_note, @project, default_enabled: true)
     push_frontend_feature_flag(:diffs_gradual_load, @project, default_enabled: true)
@@ -502,7 +502,7 @@ class Projects::MergeRequestsController < Projects::MergeRequests::ApplicationCo
     params = request.query_parameters
     params[:view] = "inline"
 
-    if Feature.enabled?(:default_merge_ref_for_diffs, project)
+    if Feature.enabled?(:default_merge_ref_for_diffs, project, default_enabled: :yaml)
       params = params.merge(diff_head: true)
     end
 

app/services/merge_requests/reload_merge_head_diff_service.rb

@@ -24,7 +24,7 @@ module MergeRequests
     attr_reader :merge_request
 
     def enabled?
-      Feature.enabled?(:default_merge_ref_for_diffs, merge_request.project)
+      Feature.enabled?(:default_merge_ref_for_diffs, merge_request.project, default_enabled: :yaml)
     end
 
     def recreate_merge_head_diff

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

@@ -78,7 +78,7 @@
       - if mr_action === "diffs"
         - add_page_startup_api_call @endpoint_metadata_url
       - params = request.query_parameters
-      - if Feature.enabled?(:default_merge_ref_for_diffs, @project)
+      - if Feature.enabled?(:default_merge_ref_for_diffs, @project, default_enabled: :yaml)
         - params = params.merge(diff_head: true)
       = render "projects/merge_requests/tabs/pane", name: "diffs", id: "js-diffs-app", class: "diffs", data: { "is-locked": @merge_request.discussion_locked?,
         endpoint: diffs_project_merge_request_path(@project, @merge_request, 'json', params),

config/feature_flags/development/default_merge_ref_for_diffs.yml

@@ -5,4 +5,4 @@ rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/276917
 milestone: '13.4'
 type: development
 group: group::code review
-default_enabled: false
+default_enabled: true