Fixed #93 Make puppet version check respect env vars

Author: Dylan Ratcliffe

lib/octocatalog-diff/catalog/computed.rb

@@ -68,7 +68,7 @@ def build(logger = Logger.new(StringIO.new))
       # @return [String] Puppet version
       def puppet_version
         raise ArgumentError, '"puppet_binary" was not passed to OctocatalogDiff::Catalog::Computed' unless @puppet_binary
-        @puppet_version ||= OctocatalogDiff::Util::PuppetVersion.puppet_version(@puppet_binary)
+        @puppet_version ||= OctocatalogDiff::Util::PuppetVersion.puppet_version(@puppet_binary, @opts)
       end
 
       # Compilation directory

lib/octocatalog-diff/util/puppetversion.rb

@@ -12,8 +12,9 @@ module Util
     class PuppetVersion
       # Determine the version of Puppet.
       # @param puppet [String] Path to Puppet binary
+      # @param options [Hash] Options hash as defined in OctocatalogDiff::Catalog::Computed
       # @return [String] Puppet version number
-      def self.puppet_version(puppet)
+      def self.puppet_version(puppet, options = {})
         raise ArgumentError, 'Puppet binary was not supplied' if puppet.nil?
         raise Errno::ENOENT, "Puppet binary #{puppet} doesn't exist" unless File.file?(puppet)
         cmdline = [Shellwords.escape(puppet), '--version'].join(' ')
@@ -24,6 +25,8 @@ def self.puppet_version(puppet)
           'PATH' => ENV['PATH'],
           'PWD' => File.dirname(puppet)
         }
+        pass_env_vars = options.fetch(:pass_env_vars, [])
+        pass_env_vars.each { |var| env[var] ||= ENV[var] }
         out, err, _status = Open3.capture3(env, cmdline, unsetenv_others: true, chdir: env['PWD'])
         return Regexp.last_match(1) if out =~ /^([\d\.]+)\s*$/
         raise "Unable to determine Puppet version: #{out} #{err}"