Add lib/hooks_utils.rb

This module is responsible for converting the GIT_PUSH_OPTION_*
environment variables into an array.

See https://gitlab.com/gitlab-org/gitlab-ce/issues/18667

lib/hooks_utils.rb

+module HooksUtils
+  extend self
+
+  # Gets an array of Git push options from the environment
+  def get_push_options
+    count = ENV['GIT_PUSH_OPTION_COUNT'].to_i
+    result = []
+
+    count.times do |i|
+      result.push(ENV["GIT_PUSH_OPTION_#{i}"])
+    end
+
+    result
+  end
+end

spec/hooks_utils_spec.rb

+require_relative 'spec_helper'
+require_relative '../lib/hooks_utils.rb'
+
+describe :get_push_options do
+  context "when GIT_PUSH_OPTION_COUNT is not set" do
+    HooksUtils.get_push_options.should == []
+  end
+
+  context "when one option is given" do
+    ENV['GIT_PUSH_OPTION_COUNT'] = '1'
+    ENV['GIT_PUSH_OPTION_0'] = 'aaa'
+    HooksUtils.get_push_options.should == ['aaa']
+  end
+
+  context "when multiple options are given" do
+    ENV['GIT_PUSH_OPTION_COUNT'] = '3'
+    ENV['GIT_PUSH_OPTION_0'] = 'aaa'
+    ENV['GIT_PUSH_OPTION_1'] = 'bbb'
+    ENV['GIT_PUSH_OPTION_2'] = 'ccc'
+    HooksUtils.get_push_options.should == ['aaa', 'bbb', 'ccc']
+  end
+end