Neovim 10 provides `vim.fs.root()`

[MartenBE]

This could probably simplify the code.

vim.fs.root({source}, {marker})                                *vim.fs.root()*
    Find the first parent directory containing a specific "marker", relative
    to a file path or buffer.

    If the buffer is unnamed (has no backing file) or has a non-empty
    'buftype' then the search begins from Nvim's |current-directory|.

    Example: >lua
        -- Find the root of a Python project, starting from file 'main.py'
        vim.fs.root(vim.fs.joinpath(vim.env.PWD, 'main.py'), {'pyproject.toml', 'setup.py' })

        -- Find the root of a git repository
        vim.fs.root(0, '.git')

        -- Find the parent directory containing any file with a .csproj extension
        vim.fs.root(0, function(name, path)
          return name:match('%.csproj$') ~= nil
        end)
<

    Attributes: ~
        Since: 0.10.0

    Parameters: ~
      • {source}  (`integer|string`) Buffer number (0 for current buffer) or
                  file path (absolute or relative to the |current-directory|)
                  to begin the search from.
      • {marker}  (`string|string[]|fun(name: string, path: string): boolean`)
                  A marker, or list of markers, to search for. If a function,
                  the function is called for each evaluated item and should
                  return true if {name} and {path} are a match.

    Return: ~
        (`string?`) Directory path containing one of the given markers, or nil
        if no directory was found.