Dear developers:

I'm using etags. I make the varivable 'tags-file-name' as buffer local, and keep its global binding value as nil. But I found when I pressing TAB key while finding tag (enter by [M-.]), etags will complete my input in the mini-buffer into some tags. At the same time, the global value of 'tags-file-name' was changed, it's not nil after the completion!!!

What should I do to keep the global value of 'tags-file-name' nil ? Or what should I do to inhibit the completion changes this variable?