Compares the git log of two branches to find tasks represented in one but not the other

finder.rb

# Very rough draft
# TODO: Clean up, extract into multiple objects and then convert to a
# gem/executable.
class TaskFinder
  def initialize(outdated_branch, updated_branch)
    @outdated_branch = outdated_branch
    @updated_branch = updated_branch
  end

  def updated_tasks_and_branches
    all_identifiers = task_number_messages + octothorpe_messages + unmerged_branches
    all_identifiers.uniq.sort_by { |identifier| [identifier.to_i, identifier.to_s] |
  end

  # Looks through commit messages that include the word "Task" and attempts
  # to extract a task number from those messages.
  private def task_number_messages
    messages = find_commit_messages('task')
    messages.reject! { |message| message.downcase.include?('merge') }
    messages.map! { |message| message[/\d+/] }
    messages.reject!(&:nil?)
    messages.uniq
  end

  # Looks through commit messages containing an octothorpe/pound
  # sign/hashtag/"#" and attempts to extract a task number from them.
  private def octothorpe_messages
    messages = find_commit_messages('\#')
    messages.map! { |message| message[/#\d+/] }
    messages.reject!(&:nil?)
    messages.map! { |message| message.delete('#') }
    messages.uniq
  end

  # Looks through merge commits (excluding those marked as merged to or from the
  # outdated_branch and those involving a remote branch) and extracts the origin
  # branch name. When the branch name includes 'task' or 'hotfix', it attempts
  # to extract a task number from the branch name and returns that instead.
  private def unmerged_branches
    messages = find_commit_messages('Merge branch')
    messages.reject! do |message|
      /Merge branch '.+' of .+ into .+/ === message || message.include?(outdated_branch)
    end
    messages.map! do |message|
      branch_name = message[/(?<=Merge branch ').+(?=')/].to_s
      task_number = ''
      if branch_name.downcase.include?('task') || branch_name.downcase.include?('hotfix')
        task_number = branch_name[/\d+/].to_s
      end
      if task_number.length > 0
        task_number
      else
        branch_name
      end
    end
    messages.uniq
  end
    
  private def find_commit_messages(grep_criterion)
    `#{log_command} | grep -i #{grep_criterion}`.split("\n").map(&:strip).freeze
  end

  private def log_command
    "git log #{outdated_branch}..#{updated_branch}".freeze
  end
end