Rakefile

#!/usr/bin/env rake
begin
  require 'bundler/setup'
rescue LoadError
  puts 'You must `gem install bundler` and `bundle install` to run rake tasks'
end

require 'date'

require 'rspec/core/rake_task'
RSpec::Core::RakeTask.new(:spec)
task :default => :spec

#############################################################################
#
# Helper functions
#
#############################################################################

def name
  @name ||= Dir['*.gemspec'].first.split('.').first
end

def version
  line = File.read("lib/#{name}.rb")[/^\s*VERSION\s*=\s*.*/]
  line.match(/.*VERSION\s*=\s*['"](.*)['"]/)[1]
end

def date
  Date.today.to_s
end

def gemspec_file
  "#{name}.gemspec"
end

def gem_file
  "#{name}-#{version}.gem"
end

def replace_header(head, header_name)
  head.sub!(/(\.#{header_name}\s*= ').*'/) { "#{$1}#{send(header_name)}'"}
end

#############################################################################
#
# Packaging tasks
#
#############################################################################

desc "Create tag v#{version} and build and push #{gem_file} to Rubygems"
task :release => :build do
  unless `git branch` =~ /^\* master$/
    puts "You must be on the master branch to release!"
    exit!
  end
  sh "git commit --allow-empty -a -m 'Release #{version}'"
  sh "git tag v#{version}"
  sh "git push origin master"
  sh "git push origin v#{version}"
  sh "gem push pkg/#{name}-#{version}.gem"
end

desc "Build #{gem_file} into the pkg directory"
task :build => :gemspec do
  sh "mkdir -p pkg"
  sh "gem build #{gemspec_file}"
  sh "mv #{gem_file} pkg"
end

desc "Generate #{gemspec_file}"
task :gemspec => :validate do
  # read spec file and split out manifest section
  spec = File.read(gemspec_file)

  # replace name version and date
  replace_header(spec, :name)
  replace_header(spec, :version)
  replace_header(spec, :date)

  # piece file back together and write
  File.open(gemspec_file, 'w') { |io| io.write(spec) }
  puts "Updated #{gemspec_file}"
end

desc "Validate #{gemspec_file}"
task :validate do
  libfiles = Dir['lib/*'] - ["lib/#{name}.rb", "lib/#{name}", "lib/tasks", "lib/generators"]
  unless libfiles.empty?
    puts "Directory `lib` should only contain a `#{name}.rb` file and `#{name}` dir."
    exit!
  end
  unless Dir['VERSION*'].empty?
    puts "A `VERSION` file at root level violates Gem best practices."
    exit!
  end
end