Add gem checksum task

Author: bf4

Rakefile

@@ -1 +1,5 @@
 require "bundler/gem_tasks"
+
+Dir['./gem_tasks/*.rake'].each do |task|
+  import(task)
+end

checksum/.gitkeep

@@ -0,0 +1,46 @@
+# see http://blog.jayfields.com/2008/02/rake-task-overwriting.html
+desc 'override bundler release task'
+task :release => ['build'] do
+  STDOUT.puts "Running Bundler Release Task Override"
+end
+require 'bundler/gem_tasks'
+
+GEMSPEC = Bundler::GemHelper.gemspec
+
+# bundler-free alternative
+# packaging
+# https://github.com/YorickPeterse/ruby-lint/blob/master/Rakefile
+# require 'rubygems/package_task'
+# GEMSPEC = Gem::Specification.load('metric_fu.gemspec')
+#
+# Gem::PackageTask.new(GEMSPEC) do |pkg|
+#   pkg.need_tar = false
+#   pkg.need_zip = false
+# end
+
+# gem signing
+# desc 'Builds and signs a new Gem'
+# task :build => [:gem] do
+#   name = "#{GEMSPEC.name}-#{GEMSPEC.version}.gem"
+#   path = File.join(File.expand_path('../../pkg', __FILE__), name)
+#
+#   sh("gem sign #{path}")
+#
+#   Rake::Task['checksum'].invoke
+# end
+
+require 'digest/sha2'
+
+desc 'Creates a SHA512 checksum of the current version'
+task :checksum => ['build']  do
+  checksums = File.expand_path('../../checksum', __FILE__)
+  name      = "#{GEMSPEC.name}-#{GEMSPEC.version}.gem"
+  path      = File.join(File.expand_path('../../pkg', __FILE__), name)
+
+  checksum_name = File.basename(path) + '.sha512'
+  checksum      = Digest::SHA512.new.hexdigest(File.read(path))
+
+  File.open(File.join(checksums, checksum_name), 'w') do |handle|
+    handle.write(checksum)
+  end
+end