http://www.clopenset.com/content/mercurial-automatic-forward-porting-script

hg-port.rb

#!/usr/bin/env ruby
require 'pathname'
require 'tempfile'

THIS_PATH = Pathname.new(__FILE__).realpath
THIS_DIR = THIS_PATH.dirname
THIS_BASE_NAME = THIS_PATH.basename

module HGHelper
  def self.run_hg(command)
    temp_file = Tempfile.new('forward-port')
    status = nil
    lines = nil
    begin
      temp_file.close
      status = system("(#{command}) > #{temp_file.path} 2>&1")
      lines = File.readlines(temp_file.path).collect(&:chomp)
    ensure
      temp_file.unlink
    end
    [status, lines]
  end
end

class Version
  include Comparable

  attr_reader :major, :minor

  def self.parse(str)
    return nil if str !~ /^v([0-9]+)\.([0-9]+)$/
    new(Integer($1), Integer($2))
  end

  def <=>(other)
    delta = major - other.major
    return 1 if delta > 0
    return -1 if delta < 0

    delta = minor - other.minor
    return 1 if delta > 0
    return -1 if delta < 0
    0
  end

  def to_s
    "v#{major}.#{minor}"
  end

  private

  def initialize(major, minor)
    @major = major
    @minor = minor
  end
end

class Options
  attr_reader :merge_version

  def self.parse(args)
    merge_version = nil
    while arg = args.shift
      case arg
      when '--merge-version' then
        temp = args.shift or raise RuntimeError.new('Value required for --merge-version')
        merge_version = Version.parse(temp) or raise RuntimeError.new("Invalid value \"#{temp}\" for --merge-version")
      else
        raise RuntimeError.new("Unsupported switch \"#{arg}\"")
      end
    end

    raise RuntimeError.new('Must specify switch --merge-version') unless merge_version

    new(merge_version)
  end

  private

  def initialize(merge_version)
    @merge_version = merge_version
  end
end

def display_output(lines)
  lines.each do |line|
    puts "> #{line}"
  end
end

def fail(message, lines)
  display_output(lines)
  raise RuntimeError.new(message)
end

def get_hg_branches(dir)
  status, lines = HGHelper.run_hg("cd #{dir}; hg branches")
  fail('hg branches failed', lines) unless status
  lines.collect { |line| line.split.first }
end

def get_versions(branches)
  branches.collect { |branch| Version.parse(branch)}.compact.sort
end

def forward_port(dir, merge_version, version)
  status, lines = HGHelper.run_hg("cd #{dir}; hg update #{version}; hg merge #{merge_version}")
  if status
    status, lines = HGHelper.run_hg("hg commit -m \"Automatic forward port from #{merge_version} to #{version}\"")
    fail('hg commit failed', lines) unless status
    puts "Changes ported from #{merge_version} to #{version}"
    true
  elsif lines.include?('abort: merging with a working directory ancestor has no effect')
    puts "No changes required porting from #{merge_version} to #{version}"
    true
  else
    display_output(lines)

    puts <<-EOS
Automatic forward port abandoned due to merge conflict.
Please resolve conflict manually and commit your changes.
Suggested commit command:

    hg commit -m "Manual forward port form #{merge_version} to #{version}"

Resume the automatic forward port with the following command:

    #{THIS_BASE_NAME} --merge-version #{version}

EOS
    false
  end
end

options = Options.parse(ARGV.clone)

versions = get_versions(get_hg_branches('.'))
raise RuntimeError.new("Version \"#{options.merge_version}\" not available") unless versions.include?(options.merge_version)

merge_and_later_versions = versions.select { |version| version >= options.merge_version }
merge_and_later_versions.each_with_index do |version, index|
  next if index == 0
  unless forward_port('.', merge_and_later_versions[index - 1], version)
    exit 1
  end
end
puts 'Done'

LICENSE

The MIT License (MIT)

Copyright (c) 2013 Richard Cook

Permission is hereby granted, free of charge, to any person obtaining a copy of
this software and associated documentation files (the "Software"), to deal in
the Software without restriction, including without limitation the rights to
use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
the Software, and to permit persons to whom the Software is furnished to do so,
subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

Now available as a gem: https://rubygems.org/gems/hg-port and https://bitbucket.org/rcook/hg-port