zhanghj <ccsmile2008@outlook.com> writes:

Hi,

> How does it work in Emacs 26/27? Why don't you let it keep the old behavior?

That time, it was unspecified, whether symlinked files/directories are
watched. Some file notification backends did, other backends didn't. In
Emacs 29, this was clarified, see (info "(elisp) File Notifications")

--8<---------------cut here---------------start------------->8---
     If FILE is a symlink, it doesn’t follow that link.  Just FILE
     itself will be watched.
--8<---------------cut here---------------end--------------->8---

There is the idea to add a new flag to the `file-notify-add-watch'
function, `follow'. This would allow to follow symlinks, with different
implementations in the different backends. Buth this hasn't been
implemented yet.

If you need this feature urgently in inotify (I guess you're using this
backend), try the appended patch in filenotify.el (untested).

Best regards, Michael.