fix: get filetype (#1258)

lua/avante/utils/init.lua

@@ -890,9 +890,19 @@ function M.is_same_file(filepath_a, filepath_b) return M.uniform_path(filepath_a
 
 function M.trim_think_content(content) return content:gsub("^<think>.-</think>", "", 1) end
 
+function M.get_filetype(filepath)
+  -- Some files are sometimes not detected correctly when buffer is not included
+  -- https://github.com/neovim/neovim/issues/27265
+
+  local buf = vim.api.nvim_create_buf(false, true)
+  local filetype = vim.filetype.match({ filename = filepath, buf = buf })
+  vim.api.nvim_buf_delete(buf, { force = true })
+
+  return filetype
+end
+
 ---@param file_path string
 ---@return string[]|nil lines
----@return string|nil file_type
 ---@return string|nil error
 function M.read_file_from_buf_or_disk(file_path)
   --- Lookup if the file is loaded in a buffer
@@ -900,8 +910,7 @@ function M.read_file_from_buf_or_disk(file_path)
   if bufnr ~= -1 and vim.api.nvim_buf_is_loaded(bufnr) then
     -- If buffer exists and is loaded, get buffer content
     local lines = vim.api.nvim_buf_get_lines(bufnr, 0, -1, false)
-    local file_type = vim.api.nvim_get_option_value("filetype", { buf = bufnr })
-    return lines, file_type, nil
+    return lines, nil
   end
 
   -- Fallback: read file from disk
@@ -909,12 +918,10 @@ function M.read_file_from_buf_or_disk(file_path)
   if file then
     local content = file:read("*all")
     file:close()
-    -- Detect the file type using the specific file's content
-    local file_type = vim.filetype.match({ filename = file_path, contents = { content } }) or "unknown"
-    return vim.split(content, "\n"), file_type, nil
+    return vim.split(content, "\n"), nil
   else
     -- M.error("failed to open file: " .. file_path .. " with error: " .. open_err)
-    return {}, nil, open_err
+    return {}, open_err
   end
 end