Conflict Manager - check git branches for conflicts early and often

check-for-rebase.rb

def check_for_rebase
  `git checkout master`
  master_sha = `git rev-parse HEAD`.strip
  @branches.delete_if do |branch, etc|
    puts `git checkout #{branch}`
    @branches[branch][:sha] = `git rev-parse HEAD`.strip

    rebased = `git rebase master 2>&1 > /dev/null`
    if rebased == ''
      puts '====> ' + branch + ' has no rebase conflicts.'
      false
    else
      puts "====> #{branch} needs to be rebased before comparing with other branches"
      `git rebase --abort`
      compare_link = branch_compare_url('master', branch)
      branch_link = branch_url(branch)
      slack_notify(email_1: etc[:author_email],
                   message: "You might want to <#{compare_link}|rebase> (or <#{branch_link}|delete>) your `#{branch}` branch in *#{@repo}*.",
                   sha1: @branches[branch][:sha],
                   sha2: master_sha)
      true
    end
  end
  puts "====> #{@branches.length} branches cleanly rebased"
end

clean-start.rb

def clean_start
  puts Dir.pwd
  puts `git checkout .`
  puts `git checkout master`
  puts `git branch --no-color | grep -v master | xargs git branch -D`
  puts `git fetch --prune`
  puts `git pull`
end

compare-branches.rb

def compare_branches
  puts '========================================='
  puts 'Ready for combinatorial branch comparison'
  puts '========================================='

  @branches.keys.combination(2).each do |alpha, beta|
    puts "compare #{alpha} with #{beta}"
    next true if already_sent?(sha1: @branches[alpha][:sha], sha2: @branches[beta][:sha])

    puts `git checkout #{alpha}`
    conflicts = `git format-patch $(git merge-base #{alpha} #{beta})..#{beta} --stdout | git apply --check - 2>&1 > /dev/null`.strip
    if conflicts.include?('patch does not apply')
      link = branch_compare_url(alpha, beta)
      slack_notify(email_1: @branches[alpha][:author_email],
                   email_2: @branches[beta][:author_email],
                   message: "Are you two working together? Because the `#{alpha}` and `#{beta}` branches of *#{@repo}* will <#{link}|conflict> with each other.",
                   sha1: @branches[alpha][:sha],
                   sha2: @branches[beta][:sha])
    else
      puts "====> #{alpha} and #{beta} are good to merge."
    end
  end
end

Jenkinsfile

// This defines a cron trigger for a scripted Jenkinsfile:
properties([pipelineTriggers([cron('*/10 8-22 * * 1-5')])])

node {
  stage('Checkout Repo with Script') {
    checkout scm
  }
  dir('conflict-checker') {
    stage('Check branches for merge conflicts') {
      // These were defined in the Jenkinsfile for my particular needs, but don't have to be.
      env.webhook_url = 'https://hooks.slack.com/services/T00000000/B00000000/XXXXXXXXXXXXXXXXXXXXXXXX'
      env.slack_channel = '#conflicts'

      // If not configured, git will complain about them missing, repeatedly.
      sh 'git config --global user.name "Jenkins Read-Only"'
      sh 'git config --global user.email "read-only@example.example"'

      sh 'ruby branch-conflict-checker.rb'
    }
  }
}

lists-of-sent-messages.rb

def store_list_of_sent_messages
  return if @new_messages.empty?

  Dir.mkdir(CACHE_DIR) unless File.exist?(CACHE_DIR)
  Dir.chdir(CACHE_DIR) do
    File.write(timestamp + '.yaml', @new_messages.to_yaml)
  end
end

def load_lists_of_sent_messages
  @new_messages = {}
  @old_messages = {}
  if File.exist?(CACHE_DIR)
    Dir.entries(CACHE_DIR).reject { |entry| ['.', '..'].include?(entry) }.each do |file|
      @old_messages.merge!(YAML.load_file(File.join(CACHE_DIR, file)))
      puts '====> Loaded message signatures from ' + file
      end
    end
  else
    puts '====> No store of sent messages found'
  end
end

def already_sent?(sha1:, sha2:)
  @old_messages[sha1 + '+' + sha2] == true || @old_messages[sha2 + '+' + sha1] == true
end

retrieve-branches.rb

def retrieve_branches
  @branches = {}
  `git for-each-ref --sort=committerdate refs/remotes --format='%(refname:short) %(authoremail)'`.lines[0...BRANCHES_TO_COMPARE].each do |line|
    remote_branch, author_email = line.split
    branch_name = remote_branch.split('/').last
    @branches[branch_name] = { author_email: author_email, remote_branch: remote_branch }
  end

  @branches.delete('master')
  @branches.delete('HEAD')
  puts "====> #{@branches.length} branches retrieved"
end

slack_notify.rb

def slack_notify(sha1:, sha2: nil, **args)
  if already_sent?(sha1: sha1, sha2: sha2)
    puts '====> Conflict previously sent to Slack.'
  else
    post_to_slack(payload: slack_payload(text: slack_text(args)))
    @new_messages[sha1 + '+' + sha2] = true
    puts '====> Conflict sent!'
  end
end

def post_to_slack(payload:)
  uri = URI.parse(ENV['webhook_url'])
  object = Net::HTTP.new(uri.host, uri.port)
  object.use_ssl = true

  object.start do |http|
    request = Net::HTTP::Post.new uri
    request.set_form_data('payload' => payload)
    response = http.request request
  end
end

def slack_payload(text:)
  <<-JSON
{
  "channel": "#{ENV['slack_channel']}",
  "username": "Conflict Management",
  "text": "#{text}"
}
  JSON
end