Returns the git tag that has the same hash as the head of the branch parameter

git.rb

require 'rubygems'
require 'git'

module Git
  class Lib
    # finds a tag with the same hash as the specified branch's head (if any)
    def tag_for_head(branch)
      tag = nil
      head_hash = command('show-ref', ['--hash', "#{branch}"])
      command('show-ref', ['--tags']).each do |r|
        if m = /^#{head_hash}\srefs\/tags\/(.*)$/.match(r)
          tag = m[1]
        end
      end
      tag
    end
  end
  class Base
    # finds a tag with the same hash as the specified branch's head (if any)
    def tag_for_head(branch='master')
      self.lib.tag_for_head(branch)
    end
  end
end