Function convert_path_to_tmpfiles_d_recurse 

pub(crate) fn convert_path_to_tmpfiles_d_recurse<U: Users, G: Groups>(
    config: &TmpfilesConvertConfig<'_, U, G>,
    out_entries: &mut BTreeSet<String>,
    out_unsupported: &mut Vec<PathBuf>,
    prefix: &mut PathBuf,
) -> Result<()>

Recursively explore target directory and translate content to tmpfiles.d entries. See convert_var_to_tmpfiles_d for more background.

This proceeds depth-first and progressively deletes translated subpaths as it goes. prefix is updated at each recursive step, so that in case of errors it can be used to pinpoint the faulty path.