git_worktree.rb

# frozen_string_literal: true
# Helper for Git worktree-aware behavior
module GitWorktree
  PROJECT_ROOT = File.expand_path("..", __dir__)

  def self.name
    return @_name if defined?(@_name)

    git_dir = `git rev-parse --git-dir 2>/dev/null`.strip
    return @_name = nil if git_dir.empty? || !git_dir.include?("/.git/worktrees/") # rubocop:disable Rails/NegateInclude

    # Conductor renames the branch after setup runs, so use the worktree directory
    # name (set at worktree creation) for a stable identifier during setup.
    @_name = normalize(File.basename(git_dir))
  end

  def self.worktree?
    !name.nil?
  end

  def self.normalize(text)
    text.gsub(/[^a-zA-Z0-9_]/, "_").squeeze("_").downcase
  end
  private_class_method :normalize

  def self.db_suffix
    value = name
    return "" if value.nil?

    "_#{value[0, 30]}"
  end

  # When in a worktree, copies each +relative_path+ from the main repo into this
  # worktree if the file is missing here but present in the main repo.
  # Safe to call without Rails loaded.
  def self.copy_from_main_worktree(*relative_paths, overwrite: false)
    git_dir = `git rev-parse --git-dir 2>/dev/null`.strip
    git_common_dir = `git rev-parse --git-common-dir 2>/dev/null`.strip
    return if git_dir.empty? || git_dir == git_common_dir

    main_root = File.expand_path("..", git_common_dir)
    require "fileutils"

    relative_paths.each do |relative_path|
      dest = File.join(PROJECT_ROOT, relative_path)
      next if File.exist?(dest) && !overwrite

      source = File.join(main_root, relative_path)
      next unless File.exist?(source)

      FileUtils.mkdir_p(File.dirname(dest))
      FileUtils.cp(source, dest)
    end
  end

  # Returns a deterministic integer from +range+ based on the current worktree branch name.
  # Returns +range.first+ when not in a worktree (e.g. main branch).
  #
  # +stride+ reserves a block of consecutive integers per worktree so callers can add an
  # offset without colliding with adjacent worktrees. For example, Capybara system tests
  # use stride equal to PARALLEL_TEST_GROUPS and add TEST_ENV_NUMBER on top:
  #
  #   GitWorktree.integer(4000..4990, stride: ENV.fetch("PARALLEL_TEST_GROUPS", 1).to_i) + ENV.fetch("TEST_ENV_NUMBER", 0).to_i
  #   # worktree A (PARALLEL_TEST_GROUPS=4) => 4000, 4001, 4002, 4003
  #   # worktree B (PARALLEL_TEST_GROUPS=4) => 4020, 4021, 4022, 4023  (never overlaps A)
  def self.integer(range, stride: 1)
    value = name
    return range.first if value.nil?

    require "zlib"
    slots = range.size / stride
    range.first + ((Zlib.crc32(value) % slots) * stride)
  end
end