(maint) Pass the appropriate Puppetfile path to module loader

Previously, we always passed the `puppetfile_name` from the `R10K::Puppetfile`
class to `R10K::ModuleLoader::Puppetfile`. That was an attempt to fix a bug
where relative Puppetfile paths were not getting resolved correctly by the
module loader (9082511).
That, however, unearthed another bug: when instantiating a new instance of
`R10K::Puppetfile` with the `puppetfile_path` option, that path would get
completely ignored in favor of the default `puppetfile_name` value. This broke
usage of the `r10k puppetfile purge` command.

This commit ensures that we pass the appropriate Puppetfile path to the module
loader - we pass the `puppetfile_path` if it exists, otherwise we pass the
`puppetfile_name`. In order to maintain the fix for the original bug around
relative Puppetfile paths, we no longer attempt to resolve the `puppetfile_path`
in the `R10K::Puppetfile` class, since `R10K::ModuleLoader::Puppetfile` already
handles that resolution.

lib/r10k/module_loader/puppetfile.rb

@@ -11,7 +11,7 @@ class Puppetfile
       DEFAULT_FORGE_API = 'forgeapi.puppetlabs.com'
 
       attr_accessor :default_branch_override, :environment
-      attr_reader :modules, :moduledir,
+      attr_reader :modules, :moduledir, :puppetfile_path,
         :managed_directories, :desired_contents, :purge_exclusions
 
       # @param basedir [String] The path that contains the moduledir &

lib/r10k/puppetfile.rb

@@ -30,10 +30,6 @@ class Puppetfile
   #   @return [String] The base directory that contains the Puppetfile
   attr_reader :basedir
 
-  # @!attrbute [r] puppetfile_path
-  #   @return [String] The path to the Puppetfile
-  attr_reader :puppetfile_path
-
   # @!attribute [r] environment
   #   @return [R10K::Environment] Optional R10K::Environment that this Puppetfile belongs to.
   attr_reader :environment
@@ -68,8 +64,9 @@ def initialize(basedir, options_or_moduledir = nil, deprecated_path_arg = nil, d
 
     @force           = deprecated_force_arg     || options.delete(:force)           || false
     @moduledir       = deprecated_moduledir_arg || options.delete(:moduledir)       || File.join(basedir, 'modules')
-    @puppetfile_name = deprecated_name_arg      || options.delete(:puppetfile_name) || 'Puppetfile'
-    @puppetfile_path = deprecated_path_arg      || options.delete(:puppetfile_path) || File.join(basedir, @puppetfile_name)
+    puppetfile_name = deprecated_name_arg      || options.delete(:puppetfile_name) || 'Puppetfile'
+    puppetfile_path = deprecated_path_arg      || options.delete(:puppetfile_path)
+    @puppetfile = puppetfile_path || puppetfile_name
     @environment     = options.delete(:environment)
 
     @overrides       = options.delete(:overrides) || {}
@@ -80,7 +77,7 @@ def initialize(basedir, options_or_moduledir = nil, deprecated_path_arg = nil, d
     @loader = ::R10K::ModuleLoader::Puppetfile.new(
       basedir: @basedir,
       moduledir: @moduledir,
-      puppetfile: @puppetfile_name,
+      puppetfile: @puppetfile,
       forge: @forge,
       overrides: @overrides,
       environment: @environment
@@ -154,6 +151,10 @@ def moduledir
     @loader.moduledir
   end
 
+  def puppetfile_path
+    @loader.puppetfile_path
+  end
+
   def environment=(env)
     @loader.environment = env
     @environment = env