nvim: Use Ruff as Python LSP

Though Ruff is not an LSP in the LSP sense but using it this way
gives us formatting and linting via code actions. All other Python
LSP servers are garbage anyway.

nvim/.config/nvim/after/ftplugin/python.lua

@@ -1,7 +1,9 @@
-vim.bo.textwidth = 0
-vim.bo.formatprg = "black -q -"
+local lsp_utils   = require('lsp-utils')
+local ruff_config = lsp_utils.ruff_config()
 
-vim.keymap.set('n', 'gq', "ggVGgq<C-o><C-o>", { noremap=true, silent=true, buffer=0 })
+vim.lsp.start(ruff_config)
+
+vim.bo.textwidth = 0
 
 vim.api.nvim_create_autocmd({ "BufWritePost" }, {
   buffer   = 0,

nvim/.config/nvim/after/plugin/nvim-lint.lua

@@ -11,7 +11,6 @@ nvim_lint.linters_by_ft = {
   javascript = { 'eslint_d' },
   lua        = { 'luacheck' },
   markdown   = { 'vale' },
-  python     = { 'ruff' },
   sh         = { 'shellcheck' },
   typescript = { 'eslint_d' },
   yaml       = { 'yamllint' },

nvim/.config/nvim/lua/lsp-utils.lua

@@ -239,6 +239,20 @@ function M.ra_config()
   }
 end
 
+function M.ruff_config()
+  local root_files     = { 'pyproject.toml', 'setup.py', 'setup.cfg', 'requirements.txt', 'Pipfile' }
+  local root_directory = get_root_directory(root_files)
+
+  return {
+    name                = "ruff",
+    cmd                 = { "ruff-lsp" },
+    filetypes           = { 'python' },
+    capabilities        = default_capabilities,
+    root_dir            = root_directory,
+    single_file_support = true,
+  }
+end
+
 function M.scheme_config()
   local root_files     = { '.git' }
   local root_directory = get_root_directory(root_files)