feat(files): make async_directory_scan a three way toggle, allowing "never" and "always", part of #236

Author: cseickel

lua/neo-tree/defaults.lua

@@ -212,7 +212,9 @@ local config = {
         ["."] = "set_root",
       }
     },
-    async_directory_scan = true, -- only applies to refreshes, it's alwsays sync when called from the Neotree commands.
+    async_directory_scan = "auto", -- "auto"   means refreshes are async, but it's synchronous when called from the Neotree commands.
+                                   -- "always" means directory scans are always async.
+                                   -- "never"  means directory scans are never async.
     bind_to_cwd = true, -- true creates a 2-way binding between vim's cwd and neo-tree's root
     -- The renderer section provides the renderers that will be used to render the tree.
     --   The first level is the node type.

lua/neo-tree/sources/filesystem/lib/fs_scan.lua

@@ -135,8 +135,12 @@ M.get_items_async = function(state, parent_id, path_to_reveal, callback)
 end
 
 M.get_items = function(state, parent_id, path_to_reveal, callback, async)
-  if type(async) == "nil" then
-    async = state.async_directory_scan
+  if state.async_directory_scan == "always" then
+    async = true
+  elseif state.async_directory_scan == "never" then
+    async = false
+  elseif type(async) == "nil" then
+    async = (state.async_directory_scan == "auto") or state.async_directory_scan
   end
 
   if not parent_id then