[denols] Fix root_dir

[e-kwsm]

At the moment denols may fail to start since root directory is not detected.

I referred to

nvim-lspconfig/lua/lspconfig/pylsp.lua

Lines 8 to 17 in b4661ec

	root_dir = function(fname)
	local root_files = {
	'pyproject.toml',
	'setup.py',
	'setup.cfg',
	'requirements.txt',
	'Pipfile',
	}
	return util.root_pattern(unpack(root_files))(fname) or util.find_git_ancestor(fname) or util.path.dirname(fname)
	end,

[mjlbach]

I'm not in favor of adding util.path.dirname as a fallback, given most deno projects should have a well defined structure. As otherwise noted, you added a redundant git check

[e-kwsm]

Without this modification, deno doesn’t start when a user writes the very first code on a project or a snippet, which is a bit inconvenient.
The behaviour is consistent with pylsp.

[mjlbach]

That's not true, the server will not start if the user does not have a root directory which is a different matter.

[e-kwsm]

I’m not sure why other servers such as pylsp and clangd are allowed to start under the cwd.

Is there something disadvantageous?

[mjlbach]

Because the configs are community contributed, and I wasn't historically as strict about undefined behavior as I'm being now.

I'll be removing those fallbacks shortly.