Gitlab: Move all issues on a (closed) milestone to a new one

gitlab_move_issues_to_new_milestone.rb

require 'bundler/inline'
gemfile do
  source 'https://rubygems.org'
  gem 'gitlab'
  gem 'pastel'
  gem 'tty-prompt'
end

require 'tty-prompt'
require 'pastel'
require 'gitlab'

Gitlab.endpoint = URL
Gitlab.private_token = TOKEN
# Milestones from this group will be scoped
TARGET_GROUP = 'developers'

p = Pastel.new

milestones = Gitlab.group_milestones(TARGET_GROUP, state: 'active').sort_by(&:due_date)

prompt = TTY::Prompt.new
choosen = prompt.select("Issues of which milestone should be transfered?") do |menu|
  milestones.each do |ms|
    menu.choice name: ms.title, value: ms
  end
end

puts " loading issues..."

issues = Gitlab.group_milestone_issues(TARGET_GROUP, choosen.id).
  auto_paginate.
  sort_by(&:web_url).
  select { |i| i.state == 'opened' }

unassigned = issues.select { |i| i.assignee.blank? }

puts "#{p.red(issues.count).to_s} open Issues found."
puts "#{p.red(unassigned.count).to_s} open issues without assignee."

target = prompt.select("Where should the issues be transfered to? ") do |menu|
  milestones.each do |ms|
    next if ms.id == choosen.id
    menu.choice name: ms.title, value: ms
  end
end

def issue_list(issue)
  p = Pastel.new
  url = sprintf("%-65s", issue.web_url)
  puts "- #{p.blue(url)} #{issue.title}"
end

puts "Transfering unassigned issues"
unassigned.each do |issue|
  issue_list(issue)
  Gitlab.edit_issue(issue.project_id, issue.iid, milestone_id: target.id)
end
puts ""
puts "Transfering assgined issues:"
issues_per_user = issues.group_by { |i| i.assignee.username }

issues_per_user.each do |username, issues|
  puts p.red(username)
  issues.each do |issue|
    issue_list(issue)
    Gitlab.edit_issue(issue.project_id, issue.iid, milestone_id: target.id)
  end
end