c
if (strbuf_avail(src) < strlen(iter->relative_path)) {
    strbuf_grow(src, strlen(iter->relative_path));
}
strbuf_addstr(src, iter->relative_path);

if (strbuf_avail(dest) < strlen(iter->relative_path)) {
    strbuf_grow(dest, strlen(iter->relative_path));
}
strbuf_addstr(dest, iter->relative_path);
