git post-receive hook for triggering Jenkins builds. Jenkins must be set up to poll the SCM, but the schedule can be empty.

post-receive-jenkins.rb

#!/usr/bin/env ruby
#
# git config --add hooks.jenkins.giturl <git url you've configured in jenkins>
# git config --add hooks.jenkins.jenkinsurl https://your.jenkins.host/

require 'rubygems'
require "net/http"
require "uri"

repopath = File.expand_path(__FILE__ + '/../../').split('/')
repopath.shift 4
reponame = repopath.join('/').gsub('.git','')
git_url = `git config hooks.jenkins.giturl 2>/dev/null`.strip
jenkins_url = `git config hooks.jenkins.jenkinsurl 2>/dev/null`.strip
if git_url.empty? or jenkins_url.empty? then
  exit 0
end

url = "#{jenkins_url}/git/notifyCommit?url=#{git_url}"
uri = URI.parse(url)
http = Net::HTTP.new(uri.host, uri.port)
if uri.scheme == "https" then
  http.use_ssl = true
  http.verify_mode = OpenSSL::SSL::VERIFY_NONE
end

request = Net::HTTP::Get.new(uri.request_uri)
response = http.request(request)
puts "jenkins: #{response.body}"