feat(event): add TreeAttachedPost (#1877)

* feat(event): add OnAttachPost

* feat(event): add TreeAttachPost

* feat(event): add TreeAttachPost

* feat(event): TreeAttachedPost fired after all mappings created, not just on_attach

doc/nvim-tree-lua.txt

@@ -1653,6 +1653,12 @@ e.g. handler for node renamed: >
                 handler parameters: ~
                   {folder_name}  `{string}` Absolute path to the removed folder.
 
+- Event.TreeAttachedPost
+                Invoked after the tree's buffer has been created and mappings
+                have been applied: |nvim-tree-mappings| or |nvim-tree.on_attach|
+                handler parameters: ~
+                  {buf}          `{number} `API buffer handle (buffer number)
+
 ==============================================================================
  9. BOOKMARKS                                            *nvim-tree-bookmarks*
 

lua/nvim-tree/events.lua

@@ -15,6 +15,7 @@ M.Event = {
   FolderCreated = "FolderCreated",
   FolderRemoved = "FolderRemoved",
   Resize = "Resize",
+  TreeAttachedPost = "TreeAttachedPost",
 }
 
 local function get_handlers(event_name)
@@ -86,6 +87,11 @@ function M._dispatch_on_tree_resize(size)
   dispatch(M.Event.Resize, size)
 end
 
+--@private
+function M._dispatch_tree_attached_post(buf)
+  dispatch(M.Event.TreeAttachedPost, buf)
+end
+
 --- @deprecated
 function M.on_nvim_tree_ready(handler)
   M.subscribe(M.Event.Ready, handler)

lua/nvim-tree/view.lua

@@ -95,6 +95,7 @@ local function create_buffer(bufnr)
   else
     require("nvim-tree.actions").apply_mappings(M.get_bufnr())
   end
+  events._dispatch_tree_attached_post(M.get_bufnr())
 end
 
 local function get_size()