bug#22736: 25.0.91; file-notify calls wrong callbacks

[Tassilo Horn]

I use inotify as `file-notify--library' on a GNU/Linux box and a very
recent emacs-25 branch version of emacs.

The problem is that when there is a directory watch on some directory
and a file watch on a file in that directory, the callback for the
directory watch gets an event with the descriptor of the file watch.

For example, here's an entry from my `file-notify-descriptors'
hashtable.

               3
               ("/home/horn/Repos/el/emacs/lisp"
                (nil . magit-filenotify--callback)
                ("filenotify.el" . auto-revert-notify-handler))

As you can see, the emacs/lisp directory is watched and changes are to
be reported to `magit-filenotify--callback'.  When that registered the
watch, it was told the descriptor is (3).

Additionally, the file filenotify.el in that directory has a watch, too.
Changes are to be handled by `auto-revert-notify-handler', and the
descriptor at registration time was the cons (3 . "filenotify.el").

So now I change filenotify.el and save.  What happens is that
`magit-filenotify--callback' is called with an event whose descriptor is
(3 . "filenotify.el").  That's wrong.  Callbacks should not have to
explicitly ignore events they haven't registered for.  And the docs also
state that the callbacks are called with events whose descriptors are
the same objects as the one returned by `file-notify-add-watch'.



In GNU Emacs 25.0.91.3 (x86_64-unknown-linux-gnu, GTK+ Version 3.18.7)
 of 2016-02-18 built on thinkpad-t440p
Repository revision: fa8fd65ef40eacb808583a968c3621c228bf021c
Windowing system distributor 'The X.Org Foundation', version 11.0.11801000
System Description:     Arch Linux

Configured using:
 'configure --with-modules --with-xwidgets 'CFLAGS=-g -ggdb3 -Og''

Configured features:
XPM JPEG TIFF GIF PNG RSVG IMAGEMAGICK SOUND GPM DBUS GCONF GSETTINGS
NOTIFY ACL GNUTLS LIBXML2 FREETYPE M17N_FLT LIBOTF XFT ZLIB
TOOLKIT_SCROLL_BARS GTK3 X11 MODULES XWIDGETS

Important settings:
  value of $LC_MONETARY: de_DE.utf8
  value of $LC_NUMERIC: de_DE.utf8
  value of $LC_TIME: de_DE.utf8
  value of $LANG: en_US.utf8
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Major mode: Summary

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  auto-compression-mode: t
  buffer-read-only: t
  column-number-mode: t
  line-number-mode: t
  transient-mark-mode: t

Recent messages:
 [2 times]
Auto-Revert mode enabled in current buffer
 [2 times]
Mark set
Quit
Contacting host: debbugs.gnu.org:80 [3 times]
20160218T194758.086> Opening nndoc server on 
/tmp/gnus-temp-group-53519uC-ephemeral...
20160218T194758.086> Opening nndoc server on 
/tmp/gnus-temp-group-53519uC-ephemeral...done
EVENT: ((3) changed "/home/horn/Repos/el/emacs/lisp/#filenotify.el#")
DATA: ("/home/horn/Repos/el/emacs/lisp/" #<buffer *magit: emacs>)

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