subroutineread_treerecursiveprivate

recursive subroutine read_tree(p, s, base, directory, location, parent, depth, pages)
    type(project_t), intent(inout), target :: p         !! the project
    type(settings_t), intent(in) :: s                   !! the settings
    type(markdown_options_t), intent(in) :: base        !! has the abbreviations of the project
    character(len=*), intent(in) :: directory           !! the directory
    character(len=*), intent(in) :: location            !! its path below the top, ending in `/`, or `''`
    integer, intent(in) :: parent                       !! the page above, or 0
    integer, intent(in) :: depth                        !! how deep it is
    type(page_t), allocatable, intent(inout) :: pages(:)    !! the pages
    type(dir_entry_t), allocatable :: entries(:)
    type(string_t), allocatable :: names(:), ordered(:), skip(:)
    character(len=:), allocatable :: name, path
    logical :: exists
    integer :: k, node, stat, index_page

    path = directory//'/index.md'
    inquire (file=path, exist=exists)
    if (.not. exists) then
        if (.not. is_input_directory(s, directory)) then
            call warn("Skipping creating page for '"//directory//"' because it does not contain 'index.md'")
        end if
        return
    end if
    call read_page(p, s, base, path, location//'index.html', parent, depth, pages, ordered, skip)
    index_page = size(pages)
    if (index_page == 0) return
    if (parent > 0 .and. pages(index_page)%parent /= parent) return
    node = index_page

    call list_directory(directory, entries, stat)
    if (stat /= 0) return
    allocate (names(0))
    do k = 1, size(ordered)
        if (ordered(k)%s /= 'index.md') call push(names, ordered(k)%s)
    end do
    block
        type(string_t), allocatable :: listed(:)
        allocate (listed(0))
        do k = 1, size(entries)
            call push(listed, entries(k)%name)
        end do
        call sort_strings(listed)
        do k = 1, size(listed)
            if (.not. contains_string(names, listed(k)%s) .and. listed(k)%s /= 'index.md') call push(names, listed(k)%s)
        end do
    end block

    do k = 1, size(names)
        name = names(k)%s
        if (name(1:1) == '.' .or. name(len(name):len(name)) == '~') cycle
        path = directory//'/'//name
        if (contains_string(skip, name)) then
            call push(pages(node)%copies, location//name)
        else if (is_directory(path)) then
            call read_tree(p, s, base, path, location//name//'/', node, depth + 1, pages)
        else if (ends_with(name, '.md')) then
            call read_page(p, s, base, path, location//page_file(name), node, depth, pages, ordered, skip)
        else
            call push(pages(node)%copies, location//name)
        end if
    end do
end subroutine read_tree