feat(clipboard): add global/universal sync option

README.md

@@ -47,11 +47,14 @@ should you!
 
 - Neo-tree won't let other buffers take over its window.
 - Neo-tree won't leave its window scrolled to the last line when there is plenty
-of room to display the whole tree.
-- Neo-tree does not need to be manually refreshed (set
-`use_libuv_file_watcher=true`)
+  of room to display the whole tree.
+- Neo-tree does not need to be manually refreshed (set `use_libuv_file_watcher =
+  true`)
 - Neo-tree can intelligently follow the current file (set
-`follow_current_file.enabled=true`)
+  `follow_current_file.enabled = true`)
+- Neo-tree can sync its clipboard across multiple instances, either globally
+  (within the same Neovim instance) or universally (across multiple Neovim
+  instances). Set `clipboard.sync = "global" | "universal"`
 - Neo-tree is thoughtful about maintaining or setting focus on the right node
 - Neo-tree windows in different tabs are completely separate
 - `respect_gitignore` actually works!
@@ -72,15 +75,19 @@ utilities, such as scanning the filesystem.
 
 There are also some optional plugins that work with Neo-tree:
 
-- [nvim-tree/nvim-web-devicons](https://github.com/nvim-tree/nvim-web-devicons) for file icons.
-- [antosha417/nvim-lsp-file-operations](https://github.com/antosha417/nvim-lsp-file-operations) for LSP-enhanced renames/etc.
-- [folke/snacks.nvim](https://github.com/folke/snacks.nvim) for image previews, see Preview Mode section.
-  - [snacks.rename](https://github.com/folke/snacks.nvim/blob/main/docs/rename.md#neo-treenvim) can also work with
-  Neo-tree
+- [nvim-tree/nvim-web-devicons](https://github.com/nvim-tree/nvim-web-devicons)
+  for file icons.
+- [antosha417/nvim-lsp-file-operations](https://github.com/antosha417/nvim-lsp-file-operations)
+  for LSP-enhanced renames/etc.
+- [folke/snacks.nvim](https://github.com/folke/snacks.nvim) for image previews,
+  see Preview Mode section.
+- [snacks.rename](https://github.com/folke/snacks.nvim/blob/main/docs/rename.md#neo-treenvim)
+  can also work with Neo-tree
 - [3rd/image.nvim](https://github.com/3rd/image.nvim) for image previews.
-  - If both snacks.nvim and image.nvim are installed. Neo-tree currently will
-  try to preview with snacks.nvim first, then try image.nvim.
-- [s1n7ax/nvim-window-picker](https://github.com/s1n7ax/nvim-window-picker) for `_with_window_picker` keymaps.
+  - If both snacks.nvim and image.nvim are installed. Neo-tree currently will try
+    to preview with snacks.nvim first, then try image.nvim.
+- [s1n7ax/nvim-window-picker](https://github.com/s1n7ax/nvim-window-picker) for
+  `_with_window_picker` keymaps.
 
 
 ### mini.deps example:

doc/neo-tree.txt

@@ -28,6 +28,7 @@ Configuration ............... |neo-tree-configuration|
   Components and Renderers .. |neo-tree-renderers|
   Buffer Variables .......... |neo-tree-buffer-variables|
   Popups .................... |neo-tree-popups|
+  Clipboard ................. |neo-tree-clipboard|
 Other Sources ............... |neo-tree-sources|
   Buffers ................... |neo-tree-buffers|
   Git Status ................ |neo-tree-git-status-source|
@@ -1912,6 +1913,17 @@ state to a string. The colors of the popup border are controlled by the
 highlight group.
 
 
+CLIPBOARD                                                   *neo-tree-clipboard*
+
+Neo-tree's clipboard can be synced globally (within the same Neovim instance) or
+universally (across multiple Neovim instances). The default is to not sync at
+all. To change this option, change the `clipboard.sync` option (options are
+`"none"|"global"|"universal"`). The universal sync option relies on a file
+located under `stdpath("state") .. "/neo-tree.nvim/clipboards"` You can also
+implement your own backend and pass it to that option as well - reading the
+source code of `require('neo-tree.clipboard')` is a good way to do it.
+
+
 ================================================================================
 OTHER SOURCES                                                                  ~
 ================================================================================

lua/neo-tree/clipboard/init.lua

@@ -0,0 +1,91 @@
+local events = require("neo-tree.events")
+local manager = require("neo-tree.sources.manager")
+local log = require("neo-tree.log")
+
+local M = {}
+
+---@enum (key) neotree.clipboard.BackendNames.Builtin
+local builtins = {
+  none = require("neo-tree.clipboard.sync.base"),
+  global = require("neo-tree.clipboard.sync.global"),
+  universal = require("neo-tree.clipboard.sync.universal"),
+}
+
+---@type table<string, neotree.clipboard.Backend?>
+M.backends = builtins
+
+---@alias neotree.Config.Clipboard.Sync neotree.clipboard.BackendNames.Builtin|neotree.clipboard.Backend
+
+---@class (exact) neotree.Config.Clipboard
+---@field sync neotree.Config.Clipboard.Sync?
+
+---@param opts neotree.Config.Clipboard
+M.setup = function(opts)
+  opts = opts or {}
+  opts.sync = opts.sync or "none"
+
+  ---@type neotree.clipboard.Backend?
+  local selected_backend
+  if type(opts.sync) == "string" then
+    selected_backend = M.backends[opts.sync]
+  elseif type(opts.sync) == "table" then
+    local sync = opts.sync
+    ---@cast sync -neotree.clipboard.BackendNames.Builtin
+    selected_backend = sync
+  end
+
+  if not selected_backend then
+    log.error("invalid clipboard sync method, disabling sync")
+    selected_backend = builtins.none
+  end
+  M.current_backend = assert(selected_backend:new())
+
+  events.subscribe({
+    event = events.STATE_CREATED,
+    ---@param new_state neotree.State
+    handler = function(new_state)
+      local clipboard, err = M.current_backend:load(new_state)
+      if not clipboard then
+        if err then
+          log.error(err)
+        end
+        return
+      end
+      new_state.clipboard = clipboard
+    end,
+  })
+
+  events.subscribe({
+    event = events.NEO_TREE_CLIPBOARD_CHANGED,
+    ---@param state neotree.State
+    handler = function(state)
+      local ok, err = M.current_backend:save(state)
+      if ok == false then
+        log.error(err)
+      end
+      M.sync_to_clipboards(state)
+    end,
+  })
+end
+
+---@param exclude_state neotree.State?
+function M.sync_to_clipboards(exclude_state)
+  -- try loading the changed clipboard into all other states
+  vim.schedule(function()
+    manager._for_each_state(nil, function(state)
+      if exclude_state == state then
+        return
+      end
+      local modified_clipboard, err = M.current_backend:load(state)
+      if not modified_clipboard then
+        if err then
+          log.error(err)
+        end
+        return
+      end
+      state.clipboard = modified_clipboard
+    end)
+  end)
+end
+
+return M

lua/neo-tree/clipboard/sync/base.lua

@@ -0,0 +1,33 @@
+---@class neotree.clipboard.Backend
+local Backend = {}
+
+---@class neotree.clipboard.Node
+---@field action string
+---@field node NuiTree.Node
+
+---@alias neotree.clipboard.Contents table<string, neotree.clipboard.Node?>
+
+---@return neotree.clipboard.Backend?
+function Backend:new()
+  local o = {}
+  setmetatable(o, self)
+  self.__index = self
+  return o
+end
+
+---Loads the clipboard from the backend
+---Return a nil clipboard to not make any changes.
+---@param state neotree.State
+---@return neotree.clipboard.Contents|false? clipboard
+---@return string? err
+function Backend:load(state) end
+
+---Writes the clipboard to the backend
+---Returns nil when nothing was saved
+---@param state neotree.State
+---@return boolean? success_or_noop
+function Backend:save(state)
+  return true
+end
+
+return Backend

lua/neo-tree/clipboard/sync/global.lua

@@ -0,0 +1,17 @@
+local Backend = require("neo-tree.clipboard.sync.base")
+local g = vim.g
+---@class neotree.clipboard.GlobalBackend : neotree.clipboard.Backend
+local GlobalBackend = Backend:new()
+
+---@type table<string, neotree.clipboard.Contents?>
+local clipboards = {}
+
+function GlobalBackend:load(state)
+  return clipboards[state.name]
+end
+
+function GlobalBackend:save(state)
+  clipboards[state.name] = state.clipboard
+end
+
+return GlobalBackend