Display stale branches oldest at the top

Currently, branches#index (overview and stale) displays the most
recent stale branch (updated 3 months ago). It's more reasonable
to display the stalest branches there instead.

app/controllers/projects/branches_controller.rb

@@ -18,8 +18,8 @@ class Projects::BranchesController < Projects::ApplicationController
   def index
     respond_to do |format|
       format.html do
-        @sort = params[:sort].presence || sort_value_recently_updated
         @mode = params[:state].presence || 'overview'
+        @sort = sort_value_for_mode
         @overview_max_branches = 5
 
         # Fetch branches for the specified mode
@@ -125,6 +125,12 @@ class Projects::BranchesController < Projects::ApplicationController
 
   private
 
+  def sort_value_for_mode
+    return params[:sort] if params[:sort].present?
+
+    'stale' == @mode ? sort_value_oldest_updated : sort_value_recently_updated
+  end
+
   # It can be expensive to calculate the diverging counts for each
   # branch. Normally the frontend should be specifying a set of branch
   # names, but prior to

spec/controllers/projects/branches_controller_spec.rb

@@ -512,7 +512,8 @@ RSpec.describe Projects::BranchesController do
               state: 'all'
             }
 
-        expect(controller.instance_variable_get(:@branch_pipeline_statuses)["master"].group).to eq("success")
+        expect(assigns[:branch_pipeline_statuses]["master"].group).to eq("success")
+        expect(assigns[:sort]).to eq('updated_desc')
       end
     end
 
@@ -543,8 +544,8 @@ RSpec.describe Projects::BranchesController do
               state: 'all'
             }
 
-        expect(controller.instance_variable_get(:@branch_pipeline_statuses)["master"].group).to eq("running")
-        expect(controller.instance_variable_get(:@branch_pipeline_statuses)["test"].group).to eq("success")
+        expect(assigns[:branch_pipeline_statuses]["master"].group).to eq("running")
+        expect(assigns[:branch_pipeline_statuses]["test"].group).to eq("success")
       end
     end
 
@@ -555,10 +556,11 @@ RSpec.describe Projects::BranchesController do
             params: {
               namespace_id: project.namespace,
               project_id: project,
-              state: 'all'
+              state: 'stale'
             }
 
-        expect(controller.instance_variable_get(:@branch_pipeline_statuses)).to be_blank
+        expect(assigns[:branch_pipeline_statuses]).to be_blank
+        expect(assigns[:sort]).to eq('updated_asc')
       end
     end
 
@@ -573,10 +575,12 @@ RSpec.describe Projects::BranchesController do
             params: {
               namespace_id: project.namespace,
               project_id: project,
+              sort: 'name_asc',
               state: 'all'
             }
 
         expect(response).to have_gitlab_http_status(:ok)
+        expect(assigns[:sort]).to eq('name_asc')
       end
     end