[Tooling] Automate Release Publishing

.buildkite/code-freeze.yml

@@ -1,7 +1,6 @@
 # yaml-language-server: $schema=https://raw.githubusercontent.com/buildkite/pipeline-schema/main/schema.json
 ---
 
-
 steps:
   - label: "Code Freeze"
     plugins: [$CI_TOOLKIT]

.buildkite/commands/checkout-release-branch.sh

@@ -1,7 +1,6 @@
 #!/bin/bash -eu
 
-# RELEASE_VERSION is passed as an environment variable from fastlane to Buildkite
-#
+# RELEASE_VERSION is passed as an environment variable passed to Buildkite by ReleasesV2.
 if [[ -z "${RELEASE_VERSION}" ]]; then
     echo "RELEASE_VERSION is not set."
     exit 1

.buildkite/complete-code-freeze.yml

@@ -1,7 +1,6 @@
 # yaml-language-server: $schema=https://raw.githubusercontent.com/buildkite/pipeline-schema/main/schema.json
 ---
 
-
 steps:
   - label: "Complete Code Freeze"
     plugins: [$CI_TOOLKIT]

.buildkite/finalize-release.yml

@@ -1,7 +1,6 @@
 # yaml-language-server: $schema=https://raw.githubusercontent.com/buildkite/pipeline-schema/main/schema.json
 ---
 
-
 steps:
   - label: "Finalize release"
     plugins: [$CI_TOOLKIT]

.buildkite/new-beta-release.yml

@@ -1,7 +1,6 @@
 # yaml-language-server: $schema=https://raw.githubusercontent.com/buildkite/pipeline-schema/main/schema.json
 ---
 
-
 steps:
   - label: "New Beta Release"
     plugins: [$CI_TOOLKIT]

.buildkite/publish-release.yml

@@ -0,0 +1,24 @@
+# yaml-language-server: $schema=https://raw.githubusercontent.com/buildkite/pipeline-schema/main/schema.json
+---
+
+steps:
+  - label: Publish Release
+    plugins: [$CI_TOOLKIT]
+    command: |
+      echo '--- :robot_face: Use bot for git operations'
+      source use-bot-for-git
+
+      echo '--- :git: Checkout Release Branch'
+      .buildkite/commands/checkout-release-branch.sh
+
+      echo '--- :ruby: Setup Ruby tools'
+      install_gems
+
+      echo '--- :package: Publish Release'
+      bundle exec fastlane publish_release skip_confirm:true
+    agents:
+       queue: tumblr-metal
+    retry:
+      manual:
+        # If those jobs fail, one should always prefer re-triggering a new build from ReleaseV2 rather than retrying the individual job from Buildkite
+        allowed: false

fastlane/lanes/release.rb

@@ -6,7 +6,6 @@
   # @param [Boolean] skip_confirm Whether to skip the confirmation prompt
   #
   # @example
-  #   bundle exec fastlane code_freeze
   #   bundle exec fastlane code_freeze skip_confirm:true
   #
   lane :code_freeze do |skip_confirm: false|
@@ -344,6 +343,47 @@
     end
   end
 
+  # This lane publishes a release on GitHub and creates a PR to backmerge the current release branch into the next release/ branch
+  #
+  # @param [Boolean] skip_confirm (default: false) If set, will skip the confirmation prompt before running the rest of the lane
+  #
+  # @example Running the lane
+  #          bundle exec fastlane publish_release skip_confirm:true
+  #
+  lane :publish_release do |skip_confirm: false|
+    ensure_git_status_clean
+    ensure_git_branch(branch: '^release/')
+
+    version_number = current_release_version
+
+    current_branch = "release/#{version_number}"
+    next_release_branch = "release/#{next_release_version}"
+
+    UI.important <<~PROMPT
+      Publish the #{version_number} release. This will:
+      - Publish the existing draft `#{version_number}` release on GitHub
+      - Which will also have GitHub create the associated git tag, pointing to the tip of the branch
+      - If the release branch for the next version `#{next_release_branch}` already exists, backmerge `#{current_branch}` into it
+      - If needed, backmerge `#{current_branch}` back into `#{DEFAULT_BRANCH}`
+      - Delete the `#{current_branch}` branch
+    PROMPT
+    UI.user_error!("Terminating as requested. Don't forget to run the remainder of this automation manually.") unless skip_confirm || UI.confirm('Do you want to continue?')
+
+    UI.important "Publishing release #{version_number} on GitHub"
+
+    publish_github_release(
+      repository: GITHUB_REPO,
+      name: version_number
+    )
+
+    create_backmerge_pr
+
+    # At this point, an intermediate branch has been created by creating a backmerge PR to a hotfix or the next version release branch.
+    # This allows us to safely delete the `release/*` branch.
+    # Note that if a hotfix or new release branches haven't been created, the backmerge PR won't be created as well.
+    delete_remote_git_branch!(current_branch)
+  end
+
   lane :check_translations_coverage do |options|
     UI.message('Checking WordPress app strings translation status...')
     check_translation_progress(
@@ -570,6 +610,14 @@ def ensure_branch_does_not_exist!(branch_name)
     UI.user_error!(error_message)
   end
 
+  # Delete a branch remotely, after having removed any GitHub branch protection
+  #
+  def delete_remote_git_branch!(branch_name)
+    remove_branch_protection(repository: GITHUB_REPO, branch: branch_name)
+
+    Git.open(Dir.pwd).push('origin', branch_name, delete: true)
+  end
+
   def report_milestone_error(error_title:)
     error_message = <<-MESSAGE
       #{error_title}