[netinstall] Allow the netinstall.yaml to contain key *groups*

- This makes it easier to just copy the example, *groups*-key
  and all, into an online YAML file and serve that up.
  You get easier (local) testing.

src/modules/netinstall/Config.cpp

@@ -109,7 +109,7 @@ Config::receivedGroupData()
 
     cDebug() << "NetInstall group data received" << m_reply->size() << "bytes from" << m_reply->url();
 
-    cqDeleter< QNetworkReply > d{ m_reply };
+    cqDeleter< QNetworkReply > d { m_reply };
 
     // If m_required is *false* then we still say we're ready
     // even if the reply is corrupt or missing.
@@ -128,11 +128,23 @@ Config::receivedGroupData()
     {
         YAML::Node groups = YAML::Load( yamlData.constData() );
 
-        if ( !groups.IsSequence() )
+        if ( groups.IsSequence() )
+        {
+            loadGroupList( CalamaresUtils::yamlSequenceToVariant( groups ) );
+        }
+        else if ( groups.IsMap() )
+        {
+            auto map = CalamaresUtils::yamlMapToVariant( groups );
+            loadGroupList( map.value( "groups" ).toList() );
+        }
+        else
         {
             cWarning() << "NetInstall groups data does not form a sequence.";
         }
-        loadGroupList( CalamaresUtils::yamlSequenceToVariant( groups ) );
+        if ( m_model->rowCount() < 1 )
+        {
+            cWarning() << "NetInstall groups data was empty.";
+        }
     }
     catch ( YAML::Exception& e )
     {

src/modules/netinstall/netinstall.conf

@@ -50,9 +50,11 @@
 #
 # The format of the groups file is the same as the format of the
 # *groups* key described below, **except** that a stand-alone
-# groups file does not have the top-level *groups* key.
-#
-# TODO: remove that ^^ restriction
+# groups file does not have to have the top-level *groups* key.
+# (It **may** have one, though, for instance when you copy
+# this configuration file to `netinstall.yaml` and key *groups*
+# must have a list-of-groups as value; if the file does not have
+# a top-level key *groups*, then the file must contain only a list of groups.
 #
 # As a special case, setting *groupsUrl* to the literal string
 # `local` means that the data is obtained from **this** config
@@ -118,9 +120,8 @@ label:
 # groups data is read from this file. The value of *groups* must be
 # a list. Each item in the list is a group (of packages, or subgroups,
 # or both). A standalone groups file contains just the list,
-# without the top-level *groups* key.
-#
-# TODO: remove that restriction ^^
+# (without the top-level *groups* key, or just the top-level *groups*
+# key and with the list as its value, like in this file).
 #
 # Using `local` is recommended only for small static package lists.
 # Here it is used for documentation purposes.