Add improved readme content for all new projects

This also introduces a new way to configure the readme template on new
project creation which can be used by other services like the
`Projects::CreateService`. It utilizes ERB for customizing the contents
of the readme templates.

Changelog: added

app/experiments/new_project_readme_content_experiment.rb

-# frozen_string_literal: true
-
-class NewProjectReadmeContentExperiment < ApplicationExperiment # rubocop:disable Gitlab/NamespacedClass
-  TEMPLATE_PATH = Rails.root.join('app', 'experiments', 'templates', 'new_project_readme_content')
-  include Rails.application.routes.url_helpers
-
-  def run_with(project, variant: nil)
-    @project = project
-    publish_to_database
-    run(variant)
-  end
-
-  def control_behavior
-    template('readme_basic.md')
-  end
-
-  def advanced_behavior
-    template('readme_advanced.md')
-  end
-
-  def redirect(to_url)
-    experiment_redirect_url(self, url: to_url)
-  end
-
-  private
-
-  def template(name)
-    ERB.new(File.read(TEMPLATE_PATH.join("#{name}.tt")), trim_mode: '<>').result(binding)
-  end
-end

app/experiments/templates/new_project_readme_content/readme_basic.md.tt

-# <%= @project.name %>
-
-<%= @project.description %>

app/services/projects/create_service.rb

@@ -167,7 +167,7 @@ module Projects
     end
 
     def readme_content
-      @readme_template.presence || experiment(:new_project_readme_content, namespace: @project.namespace).run_with(@project)
+      @readme_template.presence || ReadmeRendererService.new(@project, current_user).execute
     end
 
     def skip_wiki?

app/services/projects/readme_renderer_service.rb

+# frozen_string_literal: true
+
+module Projects
+  class ReadmeRendererService < BaseService
+    include Rails.application.routes.url_helpers
+
+    TEMPLATE_PATH = Rails.root.join('app', 'views', 'projects', 'readme_templates')
+
+    def execute
+      render(params[:template_name] || :default)
+    end
+
+    private
+
+    def render(template_name)
+      ERB.new(File.read(sanitized_filename(template_name)), trim_mode: '<>').result(binding)
+    end
+
+    def sanitized_filename(template_name)
+      path = Gitlab::Utils.check_path_traversal!("#{template_name}.md.tt")
+      path = TEMPLATE_PATH.join(path).to_s
+      Gitlab::Utils.check_allowed_absolute_path!(path, [TEMPLATE_PATH.to_s])
+
+      path
+    end
+  end
+end

app/views/projects/readme_templates/default.md.tt

+# <%= project.name %>
+
+<%= project.description %>
+
+
+## Getting started
+
+To make it easy for you to get started with GitLab, here's a list of recommended next steps.
+
+Already a pro? Just edit this README.md and make it your own. Want to make it easy? [Use the template at the bottom](#editing-this-readme)!
+
+## Add your files
+
+- [ ] [Create](https://docs.gitlab.com/ee/user/project/repository/web_editor.html#create-a-file) or [upload](https://docs.gitlab.com/ee/user/project/repository/web_editor.html#upload-a-file) files
+- [ ] [Add files using the command line](https://docs.gitlab.com/ee/gitlab-basics/add-file.html#add-a-file-using-the-command-line) or push an existing Git repository with the following command:
+
+```
+cd existing_repo
+git remote add origin <%= project.http_url_to_repo %>
+git branch -M <%= project.default_branch_or_main %>
+git push -uf origin <%= project.default_branch_or_main %>
+```
+
+## Integrate with your tools
+
+- [ ] [Set up project integrations](<%= project_settings_integrations_url(project) %>)
+
+## Collaborate with your team
+
+- [ ] [Invite team members and collaborators](https://docs.gitlab.com/ee/user/project/members/)
+- [ ] [Create a new merge request](https://docs.gitlab.com/ee/user/project/merge_requests/creating_merge_requests.html)
+- [ ] [Automatically close issues from merge requests](https://docs.gitlab.com/ee/user/project/issues/managing_issues.html#closing-issues-automatically)
+- [ ] [Enable merge request approvals](https://docs.gitlab.com/ee/user/project/merge_requests/approvals/)
+- [ ] [Automatically merge when pipeline succeeds](https://docs.gitlab.com/ee/user/project/merge_requests/merge_when_pipeline_succeeds.html)
+
+## Test and Deploy
+
+Use the built-in continuous integration in GitLab.
+
+- [ ] [Get started with GitLab CI/CD](https://docs.gitlab.com/ee/ci/quick_start/index.html)
+- [ ] [Analyze your code for known vulnerabilities with Static Application Security Testing(SAST)](https://docs.gitlab.com/ee/user/application_security/sast/)
+- [ ] [Deploy to Kubernetes, Amazon EC2, or Amazon ECS using Auto Deploy](https://docs.gitlab.com/ee/topics/autodevops/requirements.html)
+- [ ] [Use pull-based deployments for improved Kubernetes management](https://docs.gitlab.com/ee/user/clusters/agent/)
+- [ ] [Set up protected environments](https://docs.gitlab.com/ee/ci/environments/protected_environments.html)
+
+***
+
+# Editing this README
+
+When you're ready to make this README your own, just edit this file and use the handy template below (or feel free to structure it however you want - this is just a starting point!).  Thank you to [makeareadme.com](https://www.makeareadme.com/) for this template.
+
+## Suggestions for a good README
+Every project is different, so consider which of these sections apply to yours. The sections used in the template are suggestions for most open source projects. Also keep in mind that while a README can be too long and detailed, too long is better than too short. If you think your README is too long, consider utilizing another form of documentation rather than cutting out information.
+
+## Name
+Choose a self-explaining name for your project.
+
+## Description
+Let people know what your project can do specifically. Provide context and add a link to any reference visitors might be unfamiliar with. A list of Features or a Background subsection can also be added here. If there are alternatives to your project, this is a good place to list differentiating factors.
+
+## Badges
+On some READMEs, you may see small images that convey metadata, such as whether or not all the tests are passing for the project. You can use Shields to add some to your README. Many services also have instructions for adding a badge.
+
+## Visuals
+Depending on what you are making, it can be a good idea to include screenshots or even a video (you'll frequently see GIFs rather than actual videos). Tools like ttygif can help, but check out Asciinema for a more sophisticated method.
+
+## Installation
+Within a particular ecosystem, there may be a common way of installing things, such as using Yarn, NuGet, or Homebrew. However, consider the possibility that whoever is reading your README is a novice and would like more guidance. Listing specific steps helps remove ambiguity and gets people to using your project as quickly as possible. If it only runs in a specific context like a particular programming language version or operating system or has dependencies that have to be installed manually, also add a Requirements subsection.
+
+## Usage
+Use examples liberally, and show the expected output if you can. It's helpful to have inline the smallest example of usage that you can demonstrate, while providing links to more sophisticated examples if they are too long to reasonably include in the README.
+
+## Support
+Tell people where they can go to for help. It can be any combination of an issue tracker, a chat room, an email address, etc.
+
+## Roadmap
+If you have ideas for releases in the future, it is a good idea to list them in the README.
+
+## Contributing
+State if you are open to contributions and what your requirements are for accepting them.
+
+For people who want to make changes to your project, it's helpful to have some documentation on how to get started. Perhaps there is a script that they should run or some environment variables that they need to set. Make these steps explicit. These instructions could also be useful to your future self.
+
+You can also document commands to lint the code or run tests. These steps help to ensure high code quality and reduce the likelihood that the changes inadvertently break something. Having instructions for running tests is especially helpful if it requires external setup, such as starting a Selenium server for testing in a browser.
+
+## Authors and acknowledgment
+Show your appreciation to those who have contributed to the project.
+
+## License
+For open source projects, say how it is licensed.
+
+## Project status
+If you have run out of energy or time for your project, put a note at the top of the README saying that development has slowed down or stopped completely. Someone may choose to fork your project or volunteer to step in as a maintainer or owner, allowing your project to keep going. You can also make an explicit request for maintainers.

config/feature_flags/experiment/new_project_readme_content.yml

----
-name: new_project_readme_content
-introduced_by_url: 
-rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/323641
-milestone: '14.0'
-type: experiment
-group: group::adoption
-default_enabled: false

spec/experiments/new_project_readme_content_experiment_spec.rb

-# frozen_string_literal: true
-
-require 'spec_helper'
-
-RSpec.describe NewProjectReadmeContentExperiment, :experiment do
-  subject { described_class.new(namespace: project.namespace) }
-
-  let(:project) { create(:project, name: 'Experimental', description: 'An experiment project') }
-
-  it "renders the basic README" do
-    expect(subject.run_with(project)).to eq(<<~MARKDOWN.strip)
-      # Experimental
-
-      An experiment project
-    MARKDOWN
-  end
-
-  describe "the advanced variant" do
-    let(:markdown) { subject.run_with(project, variant: :advanced) }
-    let(:initial_url) { 'https://docs.gitlab.com/ee/user/project/repository/web_editor.html#create-a-file' }
-
-    it "renders the project details" do
-      expect(markdown).to include(<<~MARKDOWN.strip)
-        # Experimental
-
-        An experiment project
-
-        ## Getting started
-      MARKDOWN
-    end
-
-    it "renders redirect URLs" do
-      url = Rails.application.routes.url_helpers.experiment_redirect_url(subject, url: initial_url)
-      expect(url).to include("/-/experiment/#{subject.to_param}?")
-      expect(markdown).to include(url)
-    end
-  end
-end

spec/services/projects/create_service_spec.rb

@@ -590,58 +590,55 @@ RSpec.describe Projects::CreateService, '#execute' do
       opts[:initialize_with_readme] = '1'
     end
 
-    shared_examples 'creates README.md' do
+    shared_examples 'a repo with a README.md' do
       it { expect(project.repository.commit_count).to be(1) }
       it { expect(project.repository.readme.name).to eql('README.md') }
-      it { expect(project.repository.readme.data).to include('# GitLab') }
+      it { expect(project.repository.readme.data).to include(expected_content) }
     end
 
-    it_behaves_like 'creates README.md'
+    it_behaves_like 'a repo with a README.md' do
+      let(:expected_content) do
+        <<~MARKDOWN
+          cd existing_repo
+          git remote add origin #{project.http_url_to_repo}
+          git branch -M master
+          git push -uf origin master
+        MARKDOWN
+      end
+    end
 
-    context 'and a default_branch_name is specified' do
+    context 'and a readme_template is specified' do
       before do
-        allow(Gitlab::CurrentSettings)
-          .to receive(:default_branch_name)
-          .and_return('example_branch')
+        opts[:readme_template] = "# GitLab\nThis is customized readme."
+      end
+
+      it_behaves_like 'a repo with a README.md' do
+        let(:expected_content) { "# GitLab\nThis is customized readme." }
       end
+    end
 
-      it_behaves_like 'creates README.md'
+    context 'and a default_branch_name is specified' do
+      before do
+        allow(Gitlab::CurrentSettings).to receive(:default_branch_name).and_return('example_branch')
+      end
 
-      it 'creates README.md within the specified branch rather than master' do
+      it 'creates the correct branch' do
         branches = project.repository.branches
 
         expect(branches.size).to eq(1)
         expect(branches.collect(&:name)).to contain_exactly('example_branch')
       end
 
-      describe 'advanced readme content', experiment: :new_project_readme_content do
-        before do
-          stub_experiments(new_project_readme_content: :advanced)
-        end
-
-        it_behaves_like 'creates README.md'
-
-        it 'includes advanced content in the README.md' do
-          content = project.repository.readme.data
-          expect(content).to include <<~MARKDOWN
+      it_behaves_like 'a repo with a README.md' do
+        let(:expected_content) do
+          <<~MARKDOWN
+            cd existing_repo
             git remote add origin #{project.http_url_to_repo}
             git branch -M example_branch
             git push -uf origin example_branch
           MARKDOWN
         end
       end
-
-      context 'and readme_template is specified' do
-        before do
-          opts[:readme_template] = "# GitLab\nThis is customized template."
-        end
-
-        it_behaves_like 'creates README.md'
-
-        it 'creates README.md with specified template' do
-          expect(project.repository.readme.data).to include('This is customized template.')
-        end
-      end
     end
   end
 

spec/services/projects/readme_renderer_service_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe Projects::ReadmeRendererService, '#execute' do
+  using RSpec::Parameterized::TableSyntax
+
+  subject(:service) { described_class.new(project, nil, opts) }
+
+  let_it_be(:project) { create(:project, title: 'My Project', description: '_custom_description_') }
+
+  let(:opts) { {} }
+
+  it 'renders the an ERB readme template' do
+    expect(service.execute).to start_with(<<~MARKDOWN)
+      # My Project
+
+      _custom_description_
+
+      ## Getting started
+
+      To make it easy for you to get started with GitLab, here's a list of recommended next steps.
+
+      Already a pro? Just edit this README.md and make it your own. Want to make it easy? [Use the template at the bottom](#editing-this-readme)!
+
+      ## Add your files
+
+      - [ ] [Create](https://docs.gitlab.com/ee/user/project/repository/web_editor.html#create-a-file) or [upload](https://docs.gitlab.com/ee/user/project/repository/web_editor.html#upload-a-file) files
+      - [ ] [Add files using the command line](https://docs.gitlab.com/ee/gitlab-basics/add-file.html#add-a-file-using-the-command-line) or push an existing Git repository with the following command:
+
+      ```
+      cd existing_repo
+      git remote add origin #{project.http_url_to_repo}
+      git branch -M master
+      git push -uf origin master
+      ```
+    MARKDOWN
+  end
+
+  context 'with a custom template' do
+    before do
+      allow(File).to receive(:read).and_call_original
+    end
+
+    it 'renders that template file' do
+      opts[:template_name] = :custom_readme
+
+      expect(service).to receive(:sanitized_filename).with(:custom_readme).and_return('custom_readme.md.tt')
+      expect(File).to receive(:read).with('custom_readme.md.tt').and_return('_custom_readme_file_content_')
+      expect(service.execute).to eq('_custom_readme_file_content_')
+    end
+
+    context 'with path traversal in mind' do
+      where(:template_name, :exception, :expected_path) do
+        '../path/traversal/bad' | [Gitlab::Utils::PathTraversalAttackError, 'Invalid path'] | nil
+        '/bad/template' | [StandardError, 'path /bad/template.md.tt is not allowed'] | nil
+        'good/template' | nil | 'good/template.md.tt'
+      end
+
+      with_them do
+        it 'raises the expected exception on bad paths' do
+          opts[:template_name] = template_name
+
+          if exception
+            expect { subject.execute }.to raise_error(*exception)
+          else
+            expect(File).to receive(:read).with(described_class::TEMPLATE_PATH.join(expected_path).to_s).and_return('')
+
+            expect { subject.execute }.not_to raise_error
+          end
+        end
+      end
+    end
+  end
+end