Use full list of root markers in get_project_root. Use l:markers instead of g:gutentags_project_root as the source of project root indicators when testing parent directories. In get_project_root, the list l:markers is built up with the contents of g:gutentags_project_root and g:ctrlp_root_markers (if it exists). However, g:gutentags_project_root was used directly while testing for the presence of project root indicators (l:markers was ignored).