build-emacs-osx.rb

#!/bin/env ruby
require 'fileutils'

# Most Macs these days are dual-core machines. This should, maybe, default to 2.
print "How many cores does your system have? [1] "
cores = gets.chomp.to_i
cores = 1 if cores < 1

config_opts = ["--with-jpeg=no", "--with-gif=no", "--with-tiff=no", "--with-ns"]

source_dir = "#{ENV['HOME']}/Source"
repo_dir = "#{source_dir}/emacs"
install_dir = "#{repo_dir}/nextstep/Emacs.app"
install_target = "/Applications/Emacs.app"

def git(command); system "git #{command}"; end
def make(command); system "make #{command}"; end

unless File.directory?(repo_dir)
  puts "Need to clone emacs repo first"
  Dir.mkdir(source_dir) unless File.directory?(source_dir)
  Dir.chdir(source_dir)
  git "clone git://repo.or.cz/emacs.git"
  first_time = true
end

Dir.chdir(repo_dir)
pull = `git pull`
if (pull =~ /Already up-to-date\./) && (!first_time)
  puts "No commits to pull in. Not building."
  exit
else
  puts "There are new commits. Building."
end

make "clean"
system "./configure #{config_opts.join(' ')}"
make "-j#{cores + 1}"
make "install"

puts "Installing Emacs.app"
FileUtils.rm_rf(install_target) if File.directory?(install_target)
FileUtils.move(install_dir, "/Applications/")

puts "All done. Just run Emacs.app from your Applications folder."