gistfile1.rb

#!/usr/bin/env ruby
#
# Update your Cocoa Project build number with git HEAD

require 'osx/foundation'

INFO_PLIST_FILE = "#{Dir.pwd}/Info.plist"
BUILD_NUMBER = (`git show-ref --head --abbrev HEAD | grep -v origin | awk '{print $1}'`).chomp

info_plist = OSX::NSMutableDictionary.dictionaryWithContentsOfFile(INFO_PLIST_FILE)
info_plist.setObject_forKey(BUILD_NUMBER, "CFBundleVersion")
info_plist.writeToFile_atomically(INFO_PLIST_FILE, true);