feat: add renderer.highlight_hidden, renderer.icons.show.hidden and renderer.icons.hidden_placement for dotfile icons/highlights (#2840)

* feat(hidden_decorator): Allow hidden (dotfiles) to be highlighted, both icon and name (this not related to git highlights).

Better defaults

squashed

docs(hidden)

docs(hidden)

docs(hidden)

* fix(typo): small typo on hl groups

* feat(hidden_dotfile_highlight): make a file that has a dotfile parent be also a dotfile

* docs: update docs on hidden highlight

---------

Co-authored-by: Alexander Courtis <alex@courtis.org>

lua/nvim-tree/renderer/decorator/hidden.lua

@@ -0,0 +1,55 @@
+local HL_POSITION = require("nvim-tree.enum").HL_POSITION
+local ICON_PLACEMENT = require("nvim-tree.enum").ICON_PLACEMENT
+local explorer_node = require "nvim-tree.explorer.node"
+local Decorator = require "nvim-tree.renderer.decorator"
+
+---@class DecoratorHidden: Decorator
+---@field icon HighlightedString|nil
+local DecoratorHidden = Decorator:new()
+
+---@param opts table
+---@return DecoratorHidden
+function DecoratorHidden:new(opts)
+  local o = Decorator.new(self, {
+    enabled = true,
+    hl_pos = HL_POSITION[opts.renderer.highlight_hidden] or HL_POSITION.none,
+    icon_placement = ICON_PLACEMENT[opts.renderer.icons.hidden_placement] or ICON_PLACEMENT.none,
+  })
+  ---@cast o DecoratorHidden
+
+  if opts.renderer.icons.show.hidden then
+    o.icon = {
+      str = opts.renderer.icons.glyphs.hidden,
+      hl = { "NvimTreeHiddenIcon" },
+    }
+    o:define_sign(o.icon)
+  end
+
+  return o
+end
+
+---Hidden icon: hidden.enable, renderer.icons.show.hidden and node starts with `.` (dotfile).
+---@param node Node
+---@return HighlightedString[]|nil icons
+function DecoratorHidden:calculate_icons(node)
+  if self.enabled and explorer_node.is_dotfile(node) then
+    return { self.icon }
+  end
+end
+
+---Hidden highlight: hidden.enable, renderer.highlight_hidden and node starts with `.` (dotfile).
+---@param node Node
+---@return string|nil group
+function DecoratorHidden:calculate_highlight(node)
+  if not self.enabled or self.hl_pos == HL_POSITION.none or (not explorer_node.is_dotfile(node)) then
+    return nil
+  end
+
+  if node.nodes then
+    return "NvimTreeHiddenFolderHL"
+  else
+    return "NvimTreeHiddenFileHL"
+  end
+end
+
+return DecoratorHidden