use undef instead of '' for borgbackup::archive::stdin_cmd

manifests/archive.pp

@@ -36,7 +36,7 @@
 #   needs to be [] if stdin_cmd is used.
 # @param stdin_cmd
 #   command which is executed, stdout is used as
-#   input to backup. defaults to ''
+#   input to backup. defaults to undef
 #   do not use together with $create_excludes and $create_includes
 # @param do_prune
 #   if true, prune will be run after the create command.
@@ -80,7 +80,7 @@
   Array                    $create_options     = ['verbose', 'list', 'stats', 'show-rc', 'exclude-caches'],
   Array                    $create_excludes    = [],
   Array                    $create_includes    = [],
-  String                   $stdin_cmd          = '',
+  Optional[String[1]]      $stdin_cmd          = undef,
   Boolean                  $do_prune           = true,
   Array                    $prune_options      = ['list', 'show-rc'],
   Variant[String, Integer] $keep_last          = '',
@@ -90,7 +90,7 @@
   Variant[String, Integer] $keep_monthly       = 6,
   Variant[String, Integer] $keep_yearly        = '',
 ) {
-  if ($stdin_cmd != '' and $create_includes != []) or ($stdin_cmd != '' and $create_excludes != []) {
+  if ( ! $stdin_cmd and $create_includes != []) or ( ! $stdin_cmd  and $create_excludes != []) {
     fail('borgbackup::archive $stdin_cmd cannot be used together with $create_includes or $create_exclude')
   }
 

spec/defines/archive_spec.rb

@@ -12,7 +12,6 @@
       create_options: ['verbose', 'list', 'stats', 'show-rc', 'exclude-caches'],
       create_excludes: [],
       create_includes: [],
-      stdin_cmd: '',
       do_prune: true,
       prune_options: ['list', 'show-rc'],
       keep_last: '',

templates/archive_create.erb

@@ -6,7 +6,7 @@
 
 # Backup the most important directories into an archive named after
 # the machine this script is currently running on:
-<% if @stdin_cmd != '' -%>
+<% if @stdin_cmd -%>
 <%= @stdin_cmd %> | \
 <% end -%>
 borg create                         \
@@ -27,7 +27,7 @@ borg create                         \
 <% @create_includes.each do | include | -%>
     <%= include -%>            \
 <% end -%>
-<% if @stdin_cmd != '' -%>
+<% if ! @stdin_cmd -%>
 -
 <% end -%>