fix: fixes #79, fix second+ invocation of NeoTreeShow

lua/neo-tree/sources/filesystem/init.lua

@@ -152,21 +152,27 @@ M.follow = function(callback, force_show)
   if not utils.truthy(path_to_reveal) then
     return false
   end
+
   local state = get_state()
-  if not force_show and not renderer.window_exists(state) then
-    return false
+  local window_exists = renderer.window_exists(state)
+  if window_exists then
+    local node = state.tree and state.tree:get_node()
+    if node then
+      if node:get_id() == path_to_reveal then
+        -- already focused
+        return false
+      end
+    end
+  else
+    if not force_show then
+      return false
+    end
   end
+
   local is_in_path = path_to_reveal:sub(1, #state.path) == state.path
   if not is_in_path then
     return false
   end
-  local node = state.tree and state.tree:get_node()
-  if node then
-    if node:get_id() == path_to_reveal then
-      -- already focused
-      return false
-    end
-  end
 
   log.debug("follow file: ", path_to_reveal)
   local show_only_explicitly_opened = function()