* refactor(nvim-tree.lua): extract open_nvim_tree function and add comments

* feat(nvim-tree.lua): add auto open and auto close autocmds for NvimTree

after/plugin/nvim-tree.lua

@@ -1,12 +1,23 @@
+local function open_nvim_tree(data)
+
+  -- buffer is a real file on the disk
+  local real_file = vim.fn.filereadable(data.file) == 1
+
+  -- buffer is a [No Name]
+  local no_name = data.file == "" and vim.bo[data.buf].buftype == ""
+
+  if not real_file and not no_name then
+    return
+  end
+
+  -- open the tree, find the file but don't focus it
+  require("nvim-tree.api").tree.toggle({ focus = false, find_file = true, })
+end
+
+-- Auto open
+vim.api.nvim_create_autocmd({ "VimEnter" }, { callback = open_nvim_tree })
+
+-- Auto close
 vim.api.nvim_create_autocmd({"QuitPre"}, {
     callback = function() vim.cmd("NvimTreeClose") end,
 })
-
-
-local function open_nvim_tree()
-
-  -- open the tree
-  require("nvim-tree.api").tree.open()
-end
-
-vim.api.nvim_create_autocmd({ "VimEnter" }, { callback = open_nvim_tree })