Add create_release task

Rakefile

@@ -1,4 +1,5 @@
 require "bundler/gem_tasks"
+require "bundler/gem_helper"
 require 'rspec/core/rake_task'
 
 task :spec => 'spec:all'
@@ -28,3 +29,40 @@ namespace :spec do
   end
 end
 
+desc 'Release gem and create a release on GitHub'
+task 'create_release' => 'release' do
+  require 'octokit'
+
+  Octokit.configure do |c|
+    c.login        = `git config --get github.user`.strip
+    c.access_token = `git config --get github.token`.strip
+  end
+
+  t = Bundler::GemHelper.new
+
+  current_version  = "v#{t.gemspec.version.to_s}"
+  previous_version = ""
+  `git tag`.split(/\n/).each do |tag|
+    break if tag == current_version
+    previous_version = tag
+  end
+
+  log = `git log #{previous_version}..#{current_version} --grep=Merge`
+
+  repo = `git remote -v | grep origin`.match(/([\w-]+\/[\w-]+)\.git/)[1]
+
+  description = []
+  log.split(/commit/).each do |lines|
+    lines.match(/Merge pull request \#(\d+)/) do |m|
+      url = "https://github.com/#{repo}/pull/#{m[1]}"
+      title = Octokit.pull_request(repo, m[1]).title
+      description << "* [#{title}](#{url})"
+    end
+  end
+
+  Octokit.create_release(
+    repo,
+    current_version,
+    body: description.join("\n"),
+  )
+end