Setup forward merge

Closes gh-2228

CONTRIBUTING.adoc

@@ -25,6 +25,13 @@ If you are reporting a bug, please help to speed up problem diagnosis by providi
 information as possible. Ideally, that would include a small sample project that
 reproduces the problem.
 
+== Create your branch from the oldest maintenance branch
+
+Create your topic branch to be submitted as a pull request from the oldest impacted and supported maintenance branch.
+You can find the supported versions by looking at the https://github.com/spring-projects/spring-session/milestones[milestones page].
+Switch to a branch named `<major>.<minor>.x` from the smallest milestone in the format of `<major>.<minor>.<patch>(-<prerelease>)`.
+The spring team will ensure the code gets merged forward into additional branches.
+
 
 == Sign the Contributor License Agreement
 If you have not previously done so, please fill out and

git/hooks/forward-merge

@@ -0,0 +1,135 @@
+#!/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

git/hooks/prepare-forward-merge

@@ -0,0 +1,71 @@
+#!/usr/bin/ruby
+require 'json'
+require 'net/http'
+require 'yaml'
+require 'logger'
+
+$main_branch = "3.0.x"
+
+$log = Logger.new(STDOUT)
+$log.level = Logger::WARN
+
+def get_fixed_issues()
+  $log.debug "Searching for for forward merge"
+  rev=`git rev-parse -q --verify MERGE_HEAD`.strip
+  $log.debug "Found #{rev} from git rev-parse"
+  return nil unless rev
+  fixed = []
+  message = `git log -1 --pretty=%B #{rev}`
+  message.each_line do |line|
+    $log.debug "Checking #{line} for message"
+    fixed << line.strip if /^(?:Fixes|Closes) gh-(\d+)/.match(line)
+  end
+  $log.debug "Found fixed issues #{fixed}"
+  return fixed;
+end
+
+def rewrite_message(message_file, fixed)
+  current_branch = `git rev-parse --abbrev-ref HEAD`.strip
+  if current_branch == "main"
+    current_branch = $main_branch
+  end
+  rewritten_message = ""
+  message = File.read(message_file)
+  message.each_line do |line|
+    match = /^Merge.*branch\ '(.*)'(?:\ into\ (.*))?$/.match(line)
+    if match
+      from_branch = match[1]
+      if from_branch.include? "/"
+        from_branch = from_branch.partition("/").last
+      end
+      to_brach = match[2]
+      $log.debug "Rewriting merge message"
+      line = "Merge branch '#{from_branch}'" + (to_brach ? " into #{to_brach}\n" : "\n")
+    end
+    if fixed and line.start_with?("#")
+      $log.debug "Adding fixed"
+      rewritten_message << "\n"
+      fixed.each do |fixes|
+        rewritten_message << "#{fixes} in #{current_branch}\n"
+      end
+      fixed = nil
+    end
+    rewritten_message << line
+  end
+  return rewritten_message
+end
+
+$log.debug "Running prepare-forward-merge hook script"
+
+message_file=ARGV[0]
+message_type=ARGV[1]
+
+if message_type != "merge"
+  $log.debug "Not a merge commit"
+  exit 0;
+end
+
+$log.debug "Searching for for forward merge"
+fixed = get_fixed_issues()
+rewritten_message = rewrite_message(message_file, fixed)
+File.write(message_file, rewritten_message)