Fix infinite single line highlight bug (#45)

Author: aaronik

lua/treewalker/operations.lua

@@ -39,13 +39,14 @@ end
 ---@param hl_group string
 function M.highlight(range, duration, hl_group)
   local start_row, start_col, end_row, end_col = range[1], range[2], range[3], range[4]
-  local ns_name = "treewalker.nvim-movement-highlight-" .. util.guid()
+  local ns_prefix = "treewalker.nvim-movement-highlight-"
+  local ns_name =  ns_prefix .. util.guid()
   local local_ns_id = vim.api.nvim_create_namespace(ns_name)
 
   -- clear any previous highlights so there aren't multiple active at the same time
   -- Find them by prefix, whole local name will only be used for timeout below
   for name, id in pairs(vim.api.nvim_get_namespaces()) do
-    if name:match("^treewalker") then
+    if vim.startswith(name, ns_prefix) then
       vim.api.nvim_buf_clear_namespace(0, id, 0, -1)
     end
   end
@@ -70,7 +71,7 @@ function M.highlight(range, duration, hl_group)
 
   -- Remove the local highlight after delay
   vim.defer_fn(function()
-    vim.api.nvim_buf_clear_namespace(0, local_ns_id, start_row, end_row)
+    vim.api.nvim_buf_clear_namespace(0, local_ns_id, start_row, end_row + 1)
   end, duration)
 end