forward-merge

#!/usr/bin/ruby
require 'json'
require 'net/http'
require 'yaml'
require 'logger'

$log = Logger.new(STDOUT)
$log.level = Logger::WARN

class ForwardMerge
  attr_reader :issue, :milestone, :message, :line
  def initialize(issue, milestone, message, line)
    @issue = issue
    @milestone = milestone
    @message = message
    @line = line
  end
end

def find_forward_merges(message_file)
  $log.debug "Searching for forward merge"
  rev=`git rev-parse -q --verify MERGE_HEAD`.strip
  $log.debug "Found #{rev} from git rev-parse"
  return nil unless rev
  message = File.read(message_file)
  forward_merges = []
  message.each_line do |line|
    $log.debug "Checking #{line} for message"
    match = /^(?:Fixes|Closes) gh-(\d+) in (\d\.\d\.[\dx](?:[\.\-](?:M|RC)\d)?)$/.match(line)
    if match then
      issue = match[1]
      milestone = match[2]
      $log.debug "Matched reference to issue #{issue} in milestone #{milestone}"
      forward_merges << ForwardMerge.new(issue, milestone, message, line)
    end
  end
  $log.debug "No match in merge message" unless forward_merges
  return forward_merges
end

def get_issue(username, password, repository, number)
  $log.debug "Getting issue #{number} from GitHub repository #{repository}"
  uri = URI("https://api.github.com/repos/#{repository}/issues/#{number}")
  http = Net::HTTP.new(uri.host, uri.port)
  http.use_ssl=true
  request = Net::HTTP::Get.new(uri.path)
  request.basic_auth(username, password)
  response = http.request(request)
  $log.debug "Get HTTP response #{response.code}"
  return JSON.parse(response.body) unless response.code != '200'
  puts "Failed to retrieve issue #{number}: #{response.message}"
  exit 1
end

def find_milestone(username, password, repository, title)
  $log.debug "Finding milestone #{title} from GitHub repository #{repository}"
  uri = URI("https://api.github.com/repos/#{repository}/milestones")
  http = Net::HTTP.new(uri.host, uri.port)
  http.use_ssl=true
  request = Net::HTTP::Get.new(uri.path)
  request.basic_auth(username, password)
  response = http.request(request)
  milestones = JSON.parse(response.body)
  if title.end_with?(".x")
    prefix = title.delete_suffix('.x')
    $log.debug "Finding nearest milestone from candidates starting with #{prefix}"
    titles = milestones.map { |milestone| milestone['title'] }
    titles = titles.select{ |title| title.start_with?(prefix) unless title.end_with?('.x')}
    titles = titles.sort_by { |v| Gem::Version.new(v) }
    $log.debug "Considering candidates #{titles}"
    if(titles.empty?)
      puts "Cannot find nearest milestone for prefix #{title}"
      exit 1
    end
    title = titles.first
    $log.debug "Found nearest milestone #{title}"
  end
  milestones.each do |milestone|
    $log.debug "Considering #{milestone['title']}"
    return milestone['number'] if milestone['title'] == title
  end
  puts "Milestone #{title} not found in #{repository}"
  exit 1
end

def create_issue(username, password, repository, original, title, labels, milestone, milestone_name, dry_run)
  $log.debug "Finding forward-merge issue in GitHub repository #{repository} for '#{title}'"
  uri = URI("https://api.github.com/repos/#{repository}/issues")
  http = Net::HTTP.new(uri.host, uri.port)
  http.use_ssl=true
  request = Net::HTTP::Post.new(uri.path, 'Content-Type' => 'application/json')
  request.basic_auth(username, password)
  request.body = {
    title: title,
    labels: labels,
    milestone: milestone.to_i,
    body: "Forward port of issue ##{original} to #{milestone_name}."
  }.to_json
  if dry_run then
    puts "Dry run"
    puts "POSTing to #{uri} with body #{request.body}"
    return "dry-run"
  end
  response = JSON.parse(http.request(request).body)
  $log.debug "Created new issue #{response['number']}"
  return response['number']
end

$log.debug "Running forward-merge hook script"
message_file=ARGV[0]

forward_merges = find_forward_merges(message_file)
exit 0 unless forward_merges

$log.debug "Loading config from ~/.spring-boot/forward_merge.yml"
config = YAML.load_file(File.join(Dir.home, '.spring-boot', 'forward-merge.yml'))
username = config['github']['credentials']['username']
password = config['github']['credentials']['password']
dry_run = config['dry_run']
repository = 'spring-projects/spring-session'

forward_merges.each do |forward_merge|
  existing_issue = get_issue(username, password, repository, forward_merge.issue)
  title = existing_issue['title']
  labels = existing_issue['labels'].map { |label| label['name'] }
  labels << "status: forward-port"
  $log.debug "Processing issue '#{title}'"

  milestone = find_milestone(username, password, repository, forward_merge.milestone)
  new_issue_number = create_issue(username, password, repository, forward_merge.issue, title, labels, milestone, forward_merge.milestone, dry_run)

  puts "Created gh-#{new_issue_number} for forward port of gh-#{forward_merge.issue} into #{forward_merge.milestone}"
  rewritten_message = forward_merge.message.sub(forward_merge.line, "Closes gh-#{new_issue_number}\n")
  File.write(message_file, rewritten_message)
end