Fix tagrelative option not considered in builtin.tags (#2583)

* Fix tagrelative option not considered in builtin.tags

* Fix wrong notify name

* ctags filtering with grep or rg and normalize path

* pass stylua check

---------

Co-authored-by: James Trew <j.trew10@gmail.com>

lua/telescope/builtin/__files.lua

@@ -529,6 +529,23 @@ files.current_buffer_fuzzy_find = function(opts)
 end
 
 files.tags = function(opts)
+  -- find lines not matching tags file format (begins with !) or empty lines.
+  local tags_command = (function()
+    if 1 == vim.fn.executable "rg" then
+      return { "rg", "-H", "-N", "--no-heading", "--color", "never", "-v", "^!|^$" }
+    elseif 1 == vim.fn.executable "grep" then
+      return { "grep", "-H", "--color=never", "-v", "^!\\|^$" }
+    end
+  end)()
+
+  if not tags_command then
+    utils.notify("builtin.tags", {
+      msg = "You need to install either grep or rg",
+      level = "ERROR",
+    })
+    return
+  end
+
   local tagfiles = opts.ctags_file and { opts.ctags_file } or vim.fn.tagfiles()
   for i, ctags_file in ipairs(tagfiles) do
     tagfiles[i] = vim.fn.expand(ctags_file, true)
@@ -545,7 +562,7 @@ files.tags = function(opts)
   pickers
     .new(opts, {
       prompt_title = "Tags",
-      finder = finders.new_oneshot_job(flatten { "cat", tagfiles }, opts),
+      finder = finders.new_oneshot_job(flatten { tags_command, tagfiles }, opts),
       previewer = previewers.ctags.new(opts),
       sorter = conf.generic_sorter(opts),
       attach_mappings = function()