refacto: simplify interface of reload and explore

also make common group empty check in explorer utils

lua/nvim-tree/explorer/init.lua

@@ -19,9 +19,10 @@ function Explorer.new(cwd)
   }, Explorer)
 end
 
-function Explorer:_load(cwd, node)
+function Explorer:_load(node)
+  local cwd = node.cwd or node.link_to or node.absolute_path
   git.load_project_status(cwd, function(git_statuses)
-    M.explore(node, cwd, git_statuses)
+    M.explore(node, git_statuses)
     if type(self.init_cb) == "function" then
       self.init_cb(self)
       self.init_cb = nil
@@ -31,12 +32,12 @@ end
 
 function Explorer:expand(node)
   self.init_cb = renderer.draw
-  self:_load(node.link_to or node.absolute_path, node)
+  self:_load(node)
 end
 
 function Explorer:init(f)
   self.init_cb = f
-  self:_load(self.cwd, self)
+  self:_load(self)
 end
 
 function M.setup(opts)