Add rake task to generator release announcements

To ensure consistency, and to let users get the information they
want/need at a glance, we're introducing release announcement
templates. The Chef release team will use these tasks to generate the
release announcements before posting them to Discourse.

Signed-off-by: Tom Duffield <tom@chef.io>

Rakefile

@@ -20,3 +20,4 @@ require_relative "tasks/version"
 require_relative "tasks/bundle"
 require_relative "tasks/dependencies"
 require_relative "tasks/github_changelog_generator"
+require_relative "tasks/announce"

tasks/announce.rb

@@ -0,0 +1,58 @@
+#
+# Copyright:: Copyright (c) 2016 Chef Software Inc.
+# License:: Apache License, Version 2.0
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+require "date"
+require "erb"
+
+class ReleaseAnnouncement
+  include ERB::Util
+  attr_accessor :type, :version, :maj_minor, :date, :release_notes
+
+  def initialize(version, date, type)
+    @version = version
+    @maj_minor = version.split(".")[0..1].join(".")
+    @date = Date.parse(date) unless date.nil?
+    @release_notes = release_notes_from_file
+    @type = type
+  end
+
+  def render
+    puts "-" * 30
+    puts ERB.new(template_for(@type)).result(binding)
+    puts "-" * 30
+  end
+
+  def template_for(type)
+    File.read("tasks/templates/#{type}.md.erb")
+  end
+
+  def release_notes_from_file
+    File.read("RELEASE_NOTES.md").match(/^# ChefDK #{@maj_minor} Release notes\n\n(.*)/m)[1]
+  end
+end
+
+namespace :announce do
+  desc "Generate the Prerelease Announcement (version: X.Y.Z, release_date: YYYY-MM-DD)"
+  task :prerelease, :version, :release_date do |t, args|
+    ReleaseAnnouncement.new(args[:version], args[:release_date], "prerelease").render
+  end
+
+  desc "Generate the Release Announcement (version: X.Y.Z)"
+  task :release, :version do |t, args|
+    ReleaseAnnouncement.new(args[:version], nil, "release").render
+  end
+end

tasks/templates/prerelease.md.erb

@@ -0,0 +1,35 @@
+Ohai Chefs!
+
+We have selected <%= @version %> as our ChefDK v<%= @maj_minor %> release candidate which is scheduled for release on <%= @date.strftime('%A %B %-d, %Y') %>.
+
+# Release Highlights
+
+<%= @release_notes %>
+
+Please see the [CHANGELOG](https://github.com/chef/chef-dk/blob/master/CHANGELOG.md) for the complete list of changes.
+
+# Get the Build
+As always, you can download binaries directly from [downloads.chef.io](https://downloads.chef.io/chef-dk) or by using the new `milib-install` command line utility available in ChefDK 0.19.6 or greater.
+
+```shell
+$ mixlib-install download chefdk -v <%= @version %> -c current
+```
+
+Alternatively, you can install ChefDK using one of the following command options:
+
+```shell
+# In Shell
+$ curl https://omnitruck.chef.io/install.sh | sudo bash -s -- -P chefdk -v <%= @version %> -c current
+
+# In Windows Powershell
+. { iwr -useb https://omnitruck.chef.io/install.ps1 } | iex; install -project chefdk -version <%= @version %> -channel current
+```
+
+If you want to give this version a spin in Test Kitchen, create or add the following to a `.kitchen.local.yml` file:
+
+```yaml
+provisioner:
+  product_name: chefdk
+  channel: current
+  product_version: <%= @version %>
+```

tasks/templates/release.md.erb

@@ -0,0 +1,34 @@
+Ohai Chefs!
+
+We're happy to announce the release of ChefDK v<%= @maj_minor %>!
+
+# Release Highlights
+
+<%= @release_notes %>
+
+Please see the [CHANGELOG](https://github.com/chef/chef-dk/blob/master/CHANGELOG.md) for the complete list of changes.
+
+# Get the Build
+As always, you can download binaries directly from [downloads.chef.io](https://downloads.chef.io/chef-dk) or by using the new `milib-install` command line utility available in ChefDK 0.19.6 or greater.
+
+```shell
+$ mixlib-install download chefdk -v <%= @version %>
+```
+
+Alternatively, you can install ChefDK using one of the following command options:
+
+```shell
+# In Shell
+$ curl https://omnitruck.chef.io/install.sh | sudo bash -s -- -P chefdk -v <%= @version %>
+
+# In Windows Powershell
+. { iwr -useb https://omnitruck.chef.io/install.ps1 } | iex; install -project chefdk -version <%= @version %>
+```
+
+If you want to give this version a spin in Test Kitchen, create or add the following to a `.kitchen.local.yml` file:
+
+```yaml
+provisioner:
+  product_name: chefdk
+  product_version: <%= @version %>
+```