chore/fix: renderer module initializations

- put renderer into its own folder, extract the padding logic to make it
  reloadable. Will allow small refactorings of the rendering logic to
  make it easier to extend.
- get the icon state before each renderer reload

lua/nvim-tree/renderer/padding.lua

@@ -0,0 +1,47 @@
+local M = {}
+
+function M.get_padding(depth)
+  return string.rep(' ', depth)
+end
+
+local function get_padding_arrows(icon_state)
+  return function(depth, _, _, node)
+    if node.entries then
+      local icon = icon_state.icons.folder_icons[node.open and 'arrow_open' or 'arrow_closed']
+      return string.rep(' ', depth - 2)..icon..' '
+    end
+    return string.rep(' ', depth)
+  end
+end
+
+local function get_padding_indent_markers(depth, idx, tree, _, markers)
+  local padding = ""
+  if depth ~= 0 then
+    local rdepth = depth/2
+    markers[rdepth] = idx ~= #tree.entries
+    for i=1,rdepth do
+      if idx == #tree.entries and i == rdepth then
+        padding = padding..'└ '
+      elseif markers[i] then
+        padding = padding..'│ '
+      else
+        padding = padding..'  '
+      end
+    end
+  end
+  return padding
+end
+
+function M.reload_padding_function()
+  local icon_state = require'nvim-tree.config'.get_icon_state()
+
+  if icon_state.show_folder_icon and icon_state.show_folder_arrows then
+    M.get_padding = get_padding_arrows(icon_state)
+  end
+
+  if vim.g.nvim_tree_indent_markers == 1 then
+    M.get_padding = get_padding_indent_markers
+  end
+end
+
+return M