Git Remote Version Check [Ruby] [Sensu]

check-git-remote-version.rb

#!/usr/bin/env ruby
#
#   check-git-remote-version.rb
#
# DESCRIPTION:
#   Ensure git repo is in-sync with remote
#   This check verifies that the current version of a git repo reflects the
#   latest version of a particular ref on a named remote repository.
#
# PLATFORMS:
#   Linux
#
# DEPENDENCIES:
#   gem: sensu-plugin
#
# USAGE:
#   This will return OK if the clone at `/foo/bar` matches the version on the
#   named remote called `origin` at ref `refs/heads/master`
#     check-git-remote-version.rb -c /foo/bar -r origin -b master
#
# NOTES:
#   This check depends on the locally configured remotes rather than explicitly
#   passing the remote repository via eg command line arguments.
#
# LICENSE:
#   Michael-Keith Bernard <[email protected]>
#   Released under the same terms as Sensu (the MIT license); see LICENSE for
#   details.
#

require 'open3'
require 'sensu-plugin/check/cli'

class CheckGitRemoteVersion < Sensu::Plugin::Check::CLI
  option :checkout_dir,
    short: '-c CHECKOUT',
    long: '--checkout CHECKOUT',
    description: 'Path to local git checkout',
    required: true

  option :remote,
    short: '-r REMOTE',
    long: '--remote REMOTE',
    description: 'Git remote to check',
    default: 'origin'

  option :branch,
    short: '-b BRANCH',
    long: '--branch BRANCH',
    description: 'Remote branch that should be tracked',
    default: 'master'

  def run
    if local_version == remote_version
      ok "Local git version is up-to-date with #{remote_ref}"
    end
    critical "Local git version is out of date with #{remote_ref}! Local: #{local_version}, Remote: #{remote_version}"
  end

  def local_version
    @local_version ||= in_checkout('git', 'rev-parse', '--verify', 'HEAD') do |version|
      if present?(version)
        version.strip
      else
        "<local version unknown>"
      end
    end
  end

  def remote_version
    @remote_version ||= in_checkout('git', 'ls-remote', '--exit-code', '--heads', config[:remote], config[:branch]) do |version|
      if present?(version)
        version.strip.split[0]
      else
        '<remote version unknown>'
      end
    end
  end

  def remote_ref
    "#{config[:remote]}/#{config[:branch]}"
  end

  private
  def in_checkout(command, *args, &block)
    result = Dir.chdir(config[:checkout_dir]) do
      stdout, stderr, status = Open3.capture3(command, *args)
      if status != 0
        full_cmd = "`#{command} #{args.join(" ")}`"
        reason = if present?(stderr)
                   ", Reason: #{stderr}"
                 else
                   ""
                 end
        critical "Failed to run command: #{full_cmd}#{reason}"
      end
      stdout
    end

    block.call(result)
  end

  def present?(s)
    !(s.empty? || /\A[[:space:]]*\z/.match(s))
  end
end