install_homebrew.rb

#!/usr/bin/ruby
#
# I deliberately didn't DRY /usr/local references into a variable as this
# script will not "just work" if you change the destination directory. However
# please feel free to fork it and make that possible.
#
# If you do fork, please ensure you add a comment here that explains what the
# changes are intended to do and how well you tested them.
#
# 14th March 2010:
#   Adapted CodeButler's fork: http://gist.github.com/331512
#

module Tty extend self
  def blue; bold 34; end
  def white; bold 39; end
  def red; underline 31; end
  def reset; escape 0; end
  def bold n; escape "1;#{n}" end
  def underline n; escape "4;#{n}" end
  def escape n; "\033[#{n}m" if STDOUT.tty? end
end

class Array
  def shell_s
    cp = dup
    first = cp.shift
    cp.map{ |arg| arg.gsub " ", "\\ " }.unshift(first) * " "
  end
end

def ohai *args
  puts "#{Tty.blue}==>#{Tty.white} #{args.shell_s}#{Tty.reset}"
end

def warn warning
  puts "#{Tty.red}Warning#{Tty.reset}: #{warning.chomp}"
end

alias :system_orig :system
 
def system *args
  abort "Failed during: #{args.shell_s}" unless system_orig *args
end

def sudo *args
  args = if args.length > 1
    args.unshift "sudo"
  else
    "sudo #{args}"
  end
  ohai *args
  system *args
end

def getc  # NOTE only tested on OS X
  system "stty raw -echo"
  STDIN.getc
ensure
  system "stty -raw echo"
end

####################################################################### script
abort "/usr/local/.git already exists!" if File.directory? "/usr/local/.git"
abort "Don't run this as root!" if Process.uid == 0

ohai "This script will install:"
puts "/usr/local/bin/brew"
puts "/usr/local/Library/Formula/..."
puts "/usr/local/Library/Homebrew/..."

chmods = %w(bin etc include lib sbin share var . share/locale share/man share/info share/doc share/aclocal).
            map{ |d| "/usr/local/#{d}" }.
            select{ |d| File.directory? d and not File.writable? d }
chgrps = chmods.reject{ |d| File.stat(d).grpowned? }

unless chmods.empty?
  ohai "The following directories will be made group writable:"
  puts *chmods
end
unless chgrps.empty?
  ohai "The following directories will have their group set to #{Tty.underline 39}staff#{Tty.reset}:"
  puts *chgrps
end

puts
puts "Press enter to continue"
abort unless getc == 13

if File.directory? "/usr/local"
  sudo "/bin/chmod", "g+w", *chmods unless chmods.empty?
  # all admin users are in staff
  sudo "/usr/bin/chgrp", "staff", *chgrps unless chgrps.empty?
else
  sudo "/bin/mkdir /usr/local"
  sudo "/bin/chmod g+w /usr/local"
  # the group is set to wheel by default for some reason
  sudo "/usr/bin/chgrp staff /usr/local"
end

Dir.chdir "/usr/local" do
  ohai "Downloading and Installing Homebrew..."
  # -m to stop tar erroring out if it can't modify the mtime for root owned directories
  system "/usr/bin/curl -sfL http://github.com/mxcl/homebrew/tarball/master | /usr/bin/tar xz -m --strip 1"
end

ohai "Installation successful!"

if ENV['PATH'].split(':').include? '/usr/local/bin'
  puts "Yay! Now learn to brew:"
  puts
  puts "    brew help"
  puts
else
  warn "/usr/local/bin is not in your PATH"
end