fix: Atom feed for commit list should point to path

Previously the atom feed rendered for a given commit path would render
the root instead of the filepath.

Relates to #3051

Changelog: fixed

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

@@ -26,7 +26,7 @@
           = form_tag(project_commits_path(@project, @id), method: :get, class: 'commits-search-form js-signature-container', data: { 'signatures-path' => namespace_project_signatures_path }) do
             = search_field_tag :search, params[:search], { placeholder: _('Search by message'), id: 'commits-search', class: 'form-control gl-form-input input-short gl-mt-3 gl-sm-mt-0 gl-min-w-full', spellcheck: false }
         .control.d-none.d-md-block
-          = link_to project_commits_path(@project, @ref, rss_url_options), title: _("Commits feed"), class: 'btn gl-button btn-default btn-icon' do
+          = link_to project_commits_path(@project, @id, rss_url_options), title: _("Commits feed"), class: 'btn gl-button btn-default btn-icon' do
             = sprite_icon('rss', css_class: 'qa-rss-icon')
 
   = render_if_exists 'projects/commits/mirror_status'

spec/views/projects/commits/show.html.haml_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe 'projects/commits/show.html.haml' do
+  let(:project) { create(:project, :repository) }
+  let(:commits) { [project.commit] }
+  let(:path) { 'path/to/doc.md' }
+
+  before do
+    assign(:project, project)
+    assign(:id, path)
+    assign(:repository, project.repository)
+    assign(:commits, commits)
+    assign(:hidden_commit_count, 0)
+
+    controller.params[:controller] = 'projects/commits'
+    controller.params[:action] = 'show'
+    controller.params[:namespace_id] = project.namespace.to_param
+    controller.params[:project_id] = project.to_param
+
+    allow(view).to receive(:current_user).and_return(nil)
+    allow(view).to receive(:namespace_project_signatures_path).and_return("/")
+  end
+
+  context 'tree controls' do
+    before do
+      render
+    end
+
+    it 'renders atom feed button with matching path' do
+      expect(rendered).to have_link(href: "#{project_commits_path(project, path)}?format=atom")
+    end
+  end
+end