fix(state): resolve conflict with neo-tree.nvim

- Only restore the last winbar when the winbar was affected by barbecue
  previously.
- Do not remove the last winbar from window variables.

Related: #54, #53

lua/barbecue/ui.lua

@@ -128,7 +128,9 @@ function M.update(winnr)
     or vim.tbl_contains(config.user.exclude_filetypes, vim.bo[bufnr].filetype)
     or vim.api.nvim_win_get_config(winnr).relative ~= ""
   then
-    vim.wo[winnr].winbar = state.get_last_winbar(winnr)
+    local last_winbar = state.get_last_winbar(winnr)
+    if last_winbar ~= nil then vim.wo[winnr].winbar = last_winbar end
+
     state.clear(winnr)
 
     return

lua/barbecue/ui/state.lua

@@ -8,6 +8,10 @@ local VAR_ENTRIES = "barbecue_entries"
 ---@param winnr number
 ---@return string|nil
 function M.get_last_winbar(winnr)
+  local was_affected_ok, was_affected =
+    pcall(vim.api.nvim_win_get_var, winnr, VAR_WAS_AFFECTED)
+  if not was_affected_ok or not was_affected then return nil end
+
   local last_winbar_ok, last_winbar =
     pcall(vim.api.nvim_win_get_var, winnr, VAR_LAST_WINBAR)
 
@@ -42,9 +46,8 @@ end
 function M.save(winnr, entries)
   local was_affected_ok, was_affected =
     pcall(vim.api.nvim_win_get_var, winnr, VAR_WAS_AFFECTED)
-  if was_affected_ok and was_affected then
-    pcall(vim.api.nvim_win_del_var, winnr, VAR_LAST_WINBAR)
-  else
+
+  if not was_affected_ok or not was_affected then
     vim.api.nvim_win_set_var(winnr, VAR_WAS_AFFECTED, true)
     vim.api.nvim_win_set_var(winnr, VAR_LAST_WINBAR, vim.wo[winnr].winbar)
   end