Add ability to use lockfile directly

[jsirex]

It gives good possibility to update environment from CI server.
Method load_berksfile_lock skips all validations and uses lock file directly.
For example CI server always requires to do berks install because, some of cookbooks might be not present on CI server. Also this works much faster.

Also, I think its better to not modify or auto-complete path. Because an chef-environment.rb is a ruby file, we always able to calculate right path to Berkshelf or Berkshelf.lock.

In our case we're have environments folder in chef repo. Each environment described by 3 files:

• - berksfile
• .rb - chef environment file
• .lock - berksfile lock

staging:

source 'https://supermarket.chef.io'
source 'http://company-berkshelf-api'

group :common do
  cookbook 'proj-base'
  cookbook 'proj-java', '~> 2.0'
  cookbook 'proj-chef', '~> 0.1'
end

group :balancer do
  cookbook 'proj-haproxy', '~> 2.4'
end

staging.rb

require 'chef-berksfile-env'

name 'staging'
default_attributes(...)
override_attributes(...)
# Cookbook Constraints from Berksfile
load_berksfile File.basename(__FILE__, '.rb')
# or with this PR
# load_berksfile_lock File.basename(__FILE__, '.rb') + '.lock'

Now you can do something like:

berks install -b staging # resolve all
berks update chef -b dev # update chef on dev
knife environment from file staging.rb # apply env
berks apply staging -b staging.lock # trick to update only versions

[bbaugher]

Now that Berkshelf supports the lock file with the same name and it seems __FILE__ will resolve to the actual ruby file unlike what I thought it would be pretty easy to change the logic to expect the Berksfile to live right next to the environment with the same name as you suggest. This was what I was hoping to do originally.

I'm fine merging this though

[bbaugher]

This was released as 1.2.0 (https://rubygems.org/gems/chef-berksfile-env/versions/1.2.0)