Find the most relevant JH branch for add-jh-folder

.gitlab/ci/setup.gitlab-ci.yml

@@ -151,12 +151,15 @@ detect-previous-failed-tests:
 
 add-jh-folder:
   extends: .setup:rules:add-jh-folder
-  image: ${GITLAB_DEPENDENCY_PROXY}alpine:edge
+  image: ${GITLAB_DEPENDENCY_PROXY}ruby:2.7
   stage: prepare
   before_script:
-    - apk add --no-cache --update curl bash
+    - source ./scripts/utils.sh
+    - install_gitlab_gem
   script:
-    - curl --location -o "jh-folder.tar.gz" "https://gitlab.com/gitlab-jh/gitlab/-/archive/main-jh/gitlab-main-jh.tar.gz?path=jh"
+    - JH_BRANCH=$(./scripts/setup/find-jh-branch.rb)
+    - 'echo "JH_BRANCH: ${JH_BRANCH}"'
+    - curl --location -o "jh-folder.tar.gz" "https://gitlab.com/gitlab-jh/gitlab/-/archive/${JH_BRANCH}/gitlab-${JH_BRANCH}.tar.gz?path=jh"
     - tar -xf "jh-folder.tar.gz"
     - mv gitlab-main-jh-jh/jh/ ./
     - cp Gemfile.lock jh/

doc/development/pipelines.md

@@ -222,6 +222,13 @@ The `* as-if-jh` jobs are run in addition to the regular EE-context jobs. The `j
 The intent is to ensure that a change doesn't introduce a failure after the `gitlab-org/gitlab` project is synced to
 the `gitlab-jh/gitlab` project.
 
+### Corresponding JH branch
+
+You can create a corresponding JH branch on the `gitlab-jh/gitlab` project by
+appending `-jh` to the branch name. If a corresponding JH branch is found,
+`* as-if-jh` jobs grab the `jh` folder from the respective branch,
+rather than from the default branch.
+
 ## `undercover` RSpec test
 
 > [Introduced](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/74859) in GitLab 14.6.

scripts/setup/find-jh-branch.rb

+#!/usr/bin/env ruby
+# frozen_string_literal: true
+
+# In spec/scripts/setup/find_jh_branch_spec.rb we completely stub it
+require 'gitlab' unless Object.const_defined?(:Gitlab)
+
+require_relative '../api/default_options'
+
+class FindJhBranch
+  JH_DEFAULT_BRANCH = 'main-jh'
+  JH_PROJECT_PATH = 'gitlab-jh/gitlab'
+  BranchNotFound = Class.new(RuntimeError)
+
+  def run
+    return JH_DEFAULT_BRANCH unless merge_request?
+
+    jh_merge_request_ref_name ||
+      default_branch_merge_request_ref_name ||
+      stable_branch_merge_request_ref_name ||
+      default_branch_for_non_stable
+  end
+
+  private
+
+  def merge_request?
+    !!merge_request_id
+  end
+
+  def jh_merge_request_ref_name
+    branch_exist?(JH_PROJECT_PATH, jh_ref_name) && jh_ref_name
+  end
+
+  def default_branch_merge_request_ref_name
+    target_default_branch? && JH_DEFAULT_BRANCH
+  end
+
+  def stable_branch_merge_request_ref_name
+    target_stable_branch? && begin
+      jh_stable_branch_name = merge_request.target_branch.sub(/\-ee\z/, '-jh')
+
+      branch_exist?(JH_PROJECT_PATH, jh_stable_branch_name) &&
+        jh_stable_branch_name
+    end
+  end
+
+  def default_branch_for_non_stable
+    if target_stable_branch?
+      raise(BranchNotFound, "Cannot find a suitable JH branch")
+    else
+      JH_DEFAULT_BRANCH
+    end
+  end
+
+  def branch_exist?(project_path, branch_name)
+    !!gitlab.branch(project_path, branch_name)
+  rescue Gitlab::Error::NotFound
+    false
+  end
+
+  def target_default_branch?
+    merge_request.target_branch == default_branch
+  end
+
+  def target_stable_branch?
+    merge_request.target_branch.match?(/\A(?:\d+\-)+\d+\-stable\-ee\z/)
+  end
+
+  def ref_name
+    ENV['CI_COMMIT_REF_NAME']
+  end
+
+  def default_branch
+    ENV['CI_DEFAULT_BRANCH']
+  end
+
+  def merge_request_id
+    ENV['CI_MERGE_REQUEST_IID']
+  end
+
+  def jh_ref_name
+    "#{ref_name}-jh"
+  end
+
+  def project_id
+    API::DEFAULT_OPTIONS[:project]
+  end
+
+  def merge_request
+    @merge_request ||= gitlab.merge_request(project_id, merge_request_id)
+  end
+
+  def gitlab
+    @gitlab ||= Gitlab.client(
+      endpoint: API::DEFAULT_OPTIONS[:endpoint],
+      private_token: API::DEFAULT_OPTIONS[:api_token] || ''
+    )
+  end
+end
+
+if $0 == __FILE__
+  puts FindJhBranch.new.run
+end

spec/scripts/setup/find_jh_branch_spec.rb

+# frozen_string_literal: true
+
+require 'fast_spec_helper'
+
+# NOTE: Under the context of fast_spec_helper, when we `require 'gitlab'`
+# we do not load the Gitlab client, but our own Gitlab module.
+# Keep this in mind and just stub anything which might touch it!
+require_relative '../../../scripts/setup/find-jh-branch'
+
+RSpec.describe FindJhBranch do
+  subject { described_class.new }
+
+  describe '#run' do
+    context 'when it is not a merge request' do
+      before do
+        expect(subject).to receive(:merge_request?).and_return(false)
+      end
+
+      it 'returns JH_DEFAULT_BRANCH' do
+        expect(subject.run).to eq(described_class::JH_DEFAULT_BRANCH)
+      end
+    end
+
+    context 'when it is a merge request' do
+      let(:branch_name) { 'branch-name' }
+      let(:jh_branch_name) { 'branch-name-jh' }
+      let(:default_branch) { 'main' }
+      let(:merge_request) { double(target_branch: target_branch) }
+      let(:target_branch) { default_branch }
+
+      before do
+        expect(subject).to receive(:merge_request?).and_return(true)
+
+        expect(subject)
+          .to receive(:branch_exist?)
+          .with(described_class::JH_PROJECT_PATH, jh_branch_name)
+          .and_return(jh_branch_exist)
+
+        allow(subject).to receive(:ref_name).and_return(branch_name)
+        allow(subject).to receive(:default_branch).and_return(default_branch)
+        allow(subject).to receive(:merge_request).and_return(merge_request)
+      end
+
+      context 'when there is a corresponding JH branch' do
+        let(:jh_branch_exist) { true }
+
+        it 'returns the corresponding JH branch name' do
+          expect(subject.run).to eq(jh_branch_name)
+        end
+      end
+
+      context 'when there is no corresponding JH branch' do
+        let(:jh_branch_exist) { false }
+
+        it 'returns the default JH branch' do
+          expect(subject.run).to eq(described_class::JH_DEFAULT_BRANCH)
+        end
+
+        context 'when it is targeting a default branch' do
+          let(:target_branch) { '14-6-stable-ee' }
+          let(:jh_stable_branch_name) { '14-6-stable-jh' }
+
+          before do
+            expect(subject)
+              .to receive(:branch_exist?)
+              .with(described_class::JH_PROJECT_PATH, jh_stable_branch_name)
+              .and_return(jh_stable_branch_exist)
+          end
+
+          context 'when there is a corresponding JH stable branch' do
+            let(:jh_stable_branch_exist) { true }
+
+            it 'returns the corresponding JH stable branch' do
+              expect(subject.run).to eq(jh_stable_branch_name)
+            end
+          end
+
+          context 'when there is no corresponding JH stable branch' do
+            let(:jh_stable_branch_exist) { false }
+
+            it "raises #{described_class::BranchNotFound}" do
+              expect { subject.run }.to raise_error(described_class::BranchNotFound)
+            end
+          end
+        end
+
+        context 'when it is not targeting the default branch' do
+          let(:target_branch) { default_branch.swapcase }
+
+          it 'returns the default JH branch' do
+            expect(subject.run).to eq(described_class::JH_DEFAULT_BRANCH)
+          end
+        end
+      end
+    end
+  end
+end