git pre-commit hook for Jammit

pre_commit_hook-jammit

#!/usr/bin/env ruby

require 'rubygems'
require 'jammit'

print "Jammit check... "
status_before = %x[git status --porcelain --untracked-files=no]
Jammit.package!
status_after = %x[git status --porcelain --untracked-files=no]
jammit_files = (status_after.split("\n") - status_before.split("\n")).map { |f| f.split[1] }
unless jammit_files.empty?
  puts "FAIL"
  puts "Looks like you forgot to run jammit"
  puts "Run `git add #{jammit_files.join(' ')}` and try committing again"
  exit 1
end
puts "PASS"