Issue #39099: Add links for latest pipelines

app/controllers/projects/pipelines_controller.rb

@@ -3,6 +3,7 @@
 class Projects::PipelinesController < Projects::ApplicationController
   before_action :whitelist_query_limiting, only: [:create, :retry]
   before_action :pipeline, except: [:index, :new, :create, :charts]
+  before_action :set_pipeline_path, only: [:show]
   before_action :authorize_read_pipeline!
   before_action :authorize_read_build!, only: [:index]
   before_action :authorize_create_pipeline!, only: [:new, :create]
@@ -174,14 +175,36 @@ class Projects::PipelinesController < Projects::ApplicationController
 
   # rubocop: disable CodeReuse/ActiveRecord
   def pipeline
-    @pipeline ||= project
-                    .all_pipelines
-                    .includes(user: :status)
-                    .find_by!(id: params[:id])
-                    .present(current_user: current_user)
+    @pipeline ||= if params[:id].blank? && params[:latest]
+                    latest_pipeline
+                  else
+                    project
+                      .all_pipelines
+                      .includes(user: :status)
+                      .find_by!(id: params[:id])
+                      .present(current_user: current_user)
+                  end
   end
   # rubocop: enable CodeReuse/ActiveRecord
 
+  def set_pipeline_path
+    @pipeline_path ||= if params[:id].blank? && params[:latest]
+                         latest_project_pipelines_path(@project, params['ref'])
+                       else
+                         project_pipeline_path(@project, @pipeline)
+                       end
+  end
+
+  def latest_pipeline
+    ref = params['ref'].presence || @project.default_branch
+    sha = @project.commit(ref)&.sha
+
+    @project.ci_pipelines
+            .newest_first(ref: ref, sha: sha)
+            .first
+            &.present(current_user: current_user)
+  end
+
   def whitelist_query_limiting
     # Also see https://gitlab.com/gitlab-org/gitlab-ce/issues/42343
     Gitlab::QueryLimiting.whitelist('https://gitlab.com/gitlab-org/gitlab-ce/issues/42339')

app/views/projects/pipelines/_with_tabs.html.haml

 .tabs-holder
   %ul.pipelines-tabs.nav-links.no-top.no-bottom.mobile-separator.nav.nav-tabs
     %li.js-pipeline-tab-link
-      = link_to project_pipeline_path(@project, @pipeline), data: { target: '#js-tab-pipeline', action: 'pipelines', toggle: 'tab' }, class: 'pipeline-tab' do
+      = link_to @pipeline_path, data: { target: '#js-tab-pipeline', action: 'pipelines', toggle: 'tab' }, class: 'pipeline-tab' do
         = _('Pipeline')
     %li.js-builds-tab-link
       = link_to builds_project_pipeline_path(@project, @pipeline), data: { target: '#js-tab-builds', action: 'builds', toggle: 'tab' }, class: 'builds-tab' do

changelogs/unreleased/add_links_to_latest_pipelines.yml

+---
+title: 'Add links for latest pipelines'
+merge_request: 20865
+author: Alex Ives
+type: added

config/routes/project.rb

@@ -359,6 +359,9 @@ constraints(::Constraints::ProjectUrlConstrainer.new) do
         collection do
           resource :pipelines_settings, path: 'settings', only: [:show, :update]
           get :charts
+          scope '(*ref)', constraints: { ref: Gitlab::PathRegex.git_reference_regex } do
+            get :latest, action: :show, defaults: { latest: true }
+          end
         end
 
         member do

doc/ci/pipelines.md

@@ -377,6 +377,10 @@ This functionality is only available:
 - For users with at least Developer access.
 - If the the stage contains [manual actions](#manual-actions-from-pipeline-graphs).
 
+## Most Recent Pipeline
+
+There's a link to the latest pipeline for the last commit of a given branch at `/project/pipelines/[branch]/latest`. Also, `/project/pipelines/latest` will redirect you to the latest pipeline for the last commit on the project's default branch.
+
 ## Security on protected branches
 
 A strict security model is enforced when pipelines are executed on

spec/controllers/projects/pipelines_controller_spec.rb

@@ -397,4 +397,69 @@ describe Projects::PipelinesController do
       end
     end
   end
+
+  describe 'GET latest' do
+    let(:branch_main) { project.repository.branches[0] }
+    let(:branch_secondary) { project.repository.branches[1] }
+
+    let!(:pipeline_master) do
+      create(:ci_pipeline,
+             ref: branch_main.name,
+             sha: branch_main.target,
+             project: project)
+    end
+
+    let!(:pipeline_secondary) do
+      create(:ci_pipeline,
+             ref: branch_secondary.name,
+             sha: branch_secondary.target,
+             project: project)
+    end
+
+    before do
+      project.change_head(branch_main.name)
+      project.reload_default_branch
+    end
+
+    context 'no ref provided' do
+      it 'shows latest pipeline for the default project branch' do
+        get :show, params: { namespace_id: project.namespace, project_id: project, latest: true, ref: nil }
+
+        expect(response).to have_gitlab_http_status(200)
+        expect(assigns(:pipeline)).to have_attributes(id: pipeline_master.id)
+      end
+    end
+
+    context 'ref provided' do
+      before do
+        create(:ci_pipeline, ref: 'master', project: project)
+      end
+
+      it 'shows the latest pipeline for the provided ref' do
+        get :show, params: { namespace_id: project.namespace, project_id: project, latest: true, ref: branch_secondary.name }
+
+        expect(response).to have_gitlab_http_status(200)
+        expect(assigns(:pipeline)).to have_attributes(id: pipeline_secondary.id)
+      end
+
+      context 'newer pipeline exists for older sha' do
+        before do
+          create(:ci_pipeline, ref: branch_secondary.name, sha: project.commit(branch_secondary.name).parent, project: project)
+        end
+
+        it 'shows the provided ref with the last sha/pipeline combo' do
+          get :show, params: { namespace_id: project.namespace, project_id: project, latest: true, ref: branch_secondary.name }
+
+          expect(response).to have_gitlab_http_status(200)
+          expect(assigns(:pipeline)).to have_attributes(id: pipeline_secondary.id)
+        end
+      end
+    end
+
+    it 'renders a 404 if no pipeline is found for the ref' do
+      get :show, params: { namespace_id: project.namespace, project_id: project, ref: 'no-branch' }
+
+      expect(response).to have_gitlab_http_status(404)
+    end
+  end
 end