Support multiple versions in release announcement.

So releasing 5.1 and 5.0 together won't require manual copy
and paste.

tasks/release.rb

@@ -200,69 +200,47 @@
   task release: %w(prep_release tag push)
 end
 
-task :announce do
-  Dir.chdir("pkg/") do
-    if gem_version.segments[2] == 0 || gem_version.segments[3].is_a?(Integer)
-      # Not major releases, and not security releases
-      raise "Only valid for patch releases"
+module Announcement
+  class Version
+    def initialize(version)
+      @version, @gem_version = version, Gem::Version.new(version)
     end
 
-    sums = "$ shasum -a 256 *-#{version}.gem\n" + `shasum -a 256 *-#{version}.gem`
+    def to_s
+      @version
+    end
 
-    puts "Hi everyone,"
-    puts
+    def previous
+      @gem_version.segments[0, 3].tap { |v| v[2] -= 1 }.join(".")
+    end
 
-    puts "I am happy to announce that Rails #{version} has been released."
-    puts
+    def major_or_security?
+      @gem_version.segments[2].zero? || @gem_version.segments[3].is_a?(Integer)
+    end
+
+    def rc?
+      @version =~ /rc/
+    end
+  end
+end
+
+task :announce do
+  Dir.chdir("pkg/") do
+    versions = ENV["VERSIONS"] ? ENV["VERSIONS"].split(",") : [ version ]
+    versions = versions.sort.map { |v| Announcement::Version.new(v) }
 
-    previous_version = gem_version.segments[0, 3]
-    previous_version[2] -= 1
-    previous_version = previous_version.join(".")
+   raise "Only valid for patch releases" if versions.any?(&:major_or_security?)
 
-    if version =~ /rc/
+    if versions.any?(&:rc?)
       require "date"
       future_date = Date.today + 5
       future_date += 1 while future_date.saturday? || future_date.sunday?
 
       github_user = `git config github.user`.chomp
-
-      puts <<MSG
-If no regressions are found, expect the final release on #{future_date.strftime('%A, %B %-d, %Y')}.
-If you find one, please open an [issue on GitHub](https://github.com/rails/rails/issues/new)
-#{"and mention me (@#{github_user}) on it, " unless github_user.empty?}so that we can fix it before the final release.
-
-MSG
     end
 
-    puts <<MSG
-## CHANGES since #{previous_version}
-
-To view the changes for each gem, please read the changelogs on GitHub:
-
-MSG
-    FRAMEWORKS.sort.each do |framework|
-      puts "* [#{FRAMEWORK_NAMES[framework]} CHANGELOG](https://github.com/rails/rails/blob/v#{version}/#{framework}/CHANGELOG.md)"
-    end
-    puts <<MSG
-
-*Full listing*
-
-To see the full list of changes, [check out all the commits on
-GitHub](https://github.com/rails/rails/compare/v#{previous_version}...v#{version}).
-
-## SHA-256
-
-If you'd like to verify that your gem is the same as the one I've uploaded,
-please use these SHA-256 hashes.
-
-Here are the checksums for #{version}:
-
-```
-#{sums}
-```
-
-As always, huge thanks to the many contributors who helped with this release.
-
-MSG
+    require "erb"
+    template = File.read("../tasks/release_announcement_draft.erb")
+    puts ERB.new(template, nil, "<>").result(binding)
   end
 end

tasks/release_announcement_draft.erb

+Hi everyone,
+
+I am happy to announce that Rails <%= versions.join(" and ") %> <%= versions.size > 1 ? "have" : "has" %> been released.
+
+<% if future_date %>
+If no regressions are found, expect the final release on <%= future_date.strftime("%A, %B %-d, %Y") %>.
+If you find one, please open an [issue on GitHub](https://github.com/rails/rails/issues/new)
+<%= "and mention me (@github_user}) on it, " unless github_user.empty? %>so that we can fix it before the final release.
+<% end %>
+<% versions.each do |version| %>
+
+## CHANGES since <%= version.previous %>
+
+To view the changes for each gem, please read the changelogs on GitHub:
+  <% FRAMEWORKS.sort.each do |framework| %>
+<%= "* [#{FRAMEWORK_NAMES[framework]} CHANGELOG](https://github.com/rails/rails/blob/v#{version}/#{framework}/CHANGELOG.md)" %>
+  <% end %>
+
+*Full listing*
+
+To see the full list of changes, [check out all the commits on
+GitHub](https://github.com/rails/rails/compare/v<%= "#{version.previous}...v#{version}" %>).
+  <% end %>
+## SHA-256
+
+If you'd like to verify that your gem is the same as the one I've uploaded,
+please use these SHA-256 hashes.
+
+<% versions.each do |version| %>
+Here are the checksums for <%= version %>:
+
+```
+$ shasum -a 256 *-<%= version %>.gem
+<%= `shasum -a 256 *-#{version}.gem` %>
+```
+
+<% end %>
+As always, huge thanks to the many contributors who helped with this release.