cancel any pending builds for the current branch on circle ci

cancel_pending_builds.rb

#!/usr/bin/env ruby
require 'json'
require 'open-uri'

user = ENV['circleci_user']
project = ENV['circleci_project']
token = ENV['circleci_token']

unless user && project && token
  puts "Need Circle CI user, project and token. Use the environment variables circleci_user, circleci_project, and circleci_token"
  exit
end

builds = JSON.parse open("https://circleci.com/api/v1/project/#{user}/#{project}?circle-token=#{token}").read
current_branch = `git rev-parse --abbrev-ref HEAD`.strip

unrun_builds = builds.select{|b| b["status"] == "not_running" && b["branch"] == current_branch }

if unrun_builds.size == 0
  puts "no unrun builds for branch #{current_branch}"
  exit
end

unrun_builds.each do |build|
  build_num = build["build_num"]
  puts "cancelling build #{build_num} #{build['branch']}"
  output = `curl -X POST "https://circleci.com/api/v1/project/#{user}/#{project}/#{build_num}/cancel?circle-token=#{token}"`
end