Git pre receive hooks

Gemfile.rb

#!/usr/bin/env ruby
# From: http://rand9.com/blog/git-pre-receive-hook-for-rejecting-a-bad-gemfile/

BRANCHES = %w( master stable )
REJECT_OPTIONS = %w( git tag branch path )

old_sha, new_sha, ref = STDIN.read.split(' ')
exit 0 unless BRANCHES.include?(ref.split('/').last)

diff = %x{ git diff-index --cached --name-only #{old_sha} 2> /dev/null }
if diff.is_a?(String)
  diff = diff.split("\n")
end

if diff.detect{|file| file =~ /^Gemfile$/}
  tree = %x{ git ls-tree --full-name #{new_sha} Gemfile 2> /dev/null }.split(" ")
  contents = %x{ git cat-file blob #{tree[2]} 2> /dev/null }

  invalid_lines = contents.each_line.select do |line|
    line =~ /\b(#{REJECT_OPTIONS.join('|')})\b/
  end

  unless invalid_lines.empty?
    puts
    puts '> !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!'
    puts '> ---- PUSH REJECTED by origin ----'
    puts '>'
    puts "> You've specified an invalid option for #{invalid_lines.size} gem definitions in the Gemfile"
    puts "> Invalid options are: #{REJECT_OPTIONS.join(', ')}"
    puts '>'
    puts "> The offending gems:"
    puts ">\t" + invalid_lines.join(">\t")
    puts '>'
    puts '> To fix:'
    puts ">\t* Remove the offending options"
    puts ">\t* bundle install"
    puts ">\t* Run tests"
    puts ">\t* Ammend previous commit (git add . && git commit --amend)"
    puts ">\t* git push origin #{ref.split('/').last}"
    puts '>'
    puts '> !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!'
    puts

    exit 1
  end
end