Show the "changelog" / "releases notes" of a given repo. Relies on Pull Requests descriptions (as they are editables) and printing only when their title contains "#changelog".

changelog.rb

require 'highline/import'
require 'github_api'

login = ask("Login: ")
password = ask("Password: ") { |q| q.echo = false }
owner = ask("Repo owner: ")
repo_name = ask("Repo name: ")

def print_changelog( repo, pr )
  print_pr(repo, pr) if pr.title.gsub!(/#changelog/, '')
end


def print_pr( repo, pr )
  date_at = Date.rfc3339( pr.merged_at ? pr.merged_at : pr.updated_at )

  users = repo.pull_requests.commits( number: pr["number"]).map{ |commit| commit["author"].nil? ? "" : commit["author"]["login"] }
  users.uniq!

  puts "[" + date_at.strftime('%d/%m/%Y') + "] " + pr.title.strip.upcase
  puts "Authors: " + users.join(", ")
  puts pr.body
  puts ""
end

repo = Github.new login: login, password: password, user: owner, repo: repo_name

pull_requests = repo.pull_requests

puts "### CHANGELOG ###"
puts ""

puts "----------------"
puts "UPCOMING CHANGES"
puts ""

pull_requests.list.each{ |pr| print_changelog( repo, pr ) }


puts "----------------"
puts "RELEASED"
puts ""

pull_requests.list( state: "closed" ).each do |pr|
  if pull_requests.merged?( owner, repo_name, pr.number)
    print_changelog( repo, pr )
  end
end

Gemfile

source 'https://rubygems.org'

gem "github_api"
gem "highline"

AFAIK it lacks pagination handling.