refactor(#2886): multi instance: node class refactoring: extract links, *_git_status (#2944)

* extract DirectoryLinkNode and FileLinkNode, move Node methods to children

* temporarily move DirectoryNode methods into BaseNode for easier reviewing

* move mostly unchanged DirectoryNode methods back to BaseNode

* tidy

* git.git_status_file takes an array

* update git status of links

* luacheck hack

lua/nvim-tree/node/file-link.lua

@@ -0,0 +1,50 @@
+local git = require("nvim-tree.git")
+
+local FileNode = require("nvim-tree.node.file")
+
+---@class (exact) FileLinkNode: FileNode
+---@field link_to string absolute path
+---@field fs_stat_target uv.fs_stat.result
+local FileLinkNode = FileNode:new()
+
+---Static factory method
+---@param explorer Explorer
+---@param parent Node
+---@param absolute_path string
+---@param link_to string
+---@param name string
+---@param fs_stat uv.fs_stat.result?
+---@param fs_stat_target uv.fs_stat.result
+---@return FileLinkNode? nil on vim.loop.fs_realpath failure
+function FileLinkNode:create(explorer, parent, absolute_path, link_to, name, fs_stat, fs_stat_target)
+  local o = FileNode:create(explorer, parent, absolute_path, name, fs_stat)
+
+  o = self:new(o) --[[@as FileLinkNode]]
+
+  o.type = "link"
+  o.link_to = link_to
+  o.fs_stat_target = fs_stat_target
+
+  return o
+end
+
+-----Update the GitStatus of the target otherwise the link itself
+-----@param parent_ignored boolean
+-----@param status table|nil
+function FileLinkNode:update_git_status(parent_ignored, status)
+  self.git_status = git.git_status_file(parent_ignored, status, self.link_to, self.absolute_path)
+end
+
+---Create a sanitized partial copy of a node
+---@return FileLinkNode cloned
+function FileLinkNode:clone()
+  local clone = FileNode.clone(self) --[[@as FileLinkNode]]
+
+  clone.type = self.type
+  clone.link_to = self.link_to
+  clone.fs_stat_target = self.fs_stat_target
+
+  return clone
+end
+
+return FileLinkNode