repo group: always update fullpath group_name when changing parent

It was usually set anyway before, as the group name usually was specified
without being changed and triggered this update.

kallithea/model/repo_group.py

@@ -286,6 +286,7 b' class RepoGroupModel(object):'
             if 'parent_group_id' in repo_group_args:
                 assert repo_group_args['parent_group_id'] != '-1', repo_group_args  # RepoGroupForm should have converted to None
                 repo_group.parent_group = db.RepoGroup.get(repo_group_args['parent_group_id'])
+                repo_group.group_name = repo_group.get_new_name(repo_group.name)
             if 'group_name' in repo_group_args:
                 group_name = repo_group_args['group_name']
                 if kallithea.lib.utils2.repo_name_slug(group_name) != group_name: